diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
index 4d0245b159..378612717c 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
@@ -33,6 +33,8 @@ else cast()
 
 public fun <T> AnyRow.cast(): DataRow<T> = this as DataRow<T>
 
+public fun <T, G> GroupBy<*, *>.cast(): GroupBy<T, G> = this as GroupBy<T, G>
+
 public inline fun <reified T> AnyRow.cast(verify: Boolean = true): DataRow<T> = df().cast<T>(verify)[0]
 
 public fun <T> AnyCol.cast(): DataColumn<T> = this as DataColumn<T>
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
index 4ec4202584..a34545fe16 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
@@ -7,6 +7,7 @@ import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkersExtractor
 import org.jetbrains.kotlinx.dataframe.codeGen.NameNormalizer
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.CodeGeneratorImpl
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.FullyQualifiedNames
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ShortNames
@@ -22,7 +23,7 @@ public enum class InterfaceGenerationMode {
     None;
 }
 
-public data class CodeGenResult(val code: CodeWithConverter, val newMarkers: List<Marker>)
+public data class CodeGenResult(val code: CodeWithConverter<ProvidedCodeConverter>, val newMarkers: List<Marker>)
 
 public interface CodeGenerator : ExtensionsCodeGenerator {
 
@@ -43,7 +44,7 @@ public interface CodeGenerator : ExtensionsCodeGenerator {
         interfaceMode: InterfaceGenerationMode,
         extensionProperties: Boolean,
         readDfMethod: DefaultReadDfMethod? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<ProvidedCodeConverter>
 
     public companion object {
         public fun create(useFqNames: Boolean = true): CodeGenerator {
@@ -61,7 +62,7 @@ internal fun CodeGenerator.generate(
     markerClass: KClass<*>,
     interfaceMode: InterfaceGenerationMode,
     extensionProperties: Boolean,
-): CodeWithConverter = generate(
+): CodeWithConverter<ProvidedCodeConverter> = generate(
     MarkersExtractor.get(markerClass),
     interfaceMode,
     extensionProperties
@@ -70,4 +71,4 @@ internal fun CodeGenerator.generate(
 public inline fun <reified T> CodeGenerator.generate(
     interfaceMode: InterfaceGenerationMode,
     extensionProperties: Boolean,
-): CodeWithConverter = generate(T::class, interfaceMode, extensionProperties)
+): CodeWithConverter<ProvidedCodeConverter> = generate(T::class, interfaceMode, extensionProperties)
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
index dd48b739f4..9bbe416142 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
@@ -7,14 +7,19 @@ import org.jetbrains.kotlinx.jupyter.api.VariableName
  * Class representing generated code declarations for a [Marker].
  *
  * @param declarations The generated code.
+ * @param converter Needs to provide additional info (name) from org.jetbrains.dataframe.impl.codeGen.CodeGenerator to its callers
+ * But at the same time name doesn't make sense for GroupBy where code to be executed contains two declarations
  * @param converter Optional converter for the [Marker], such as a [org.jetbrains.kotlinx.dataframe.api.cast], often used for Jupyter.
  */
-public data class CodeWithConverter(val declarations: Code, val converter: (VariableName) -> Code = EmptyConverter) {
+public data class CodeWithConverter<T : CodeConverter>(
+    val declarations: Code,
+    val converter: T
+) {
 
     public companion object {
         public const val EmptyDeclarations: Code = ""
-        public val EmptyConverter: (VariableName) -> Code = { it }
-        public val Empty: CodeWithConverter = CodeWithConverter(EmptyDeclarations, EmptyConverter)
+        public val EmptyConverter: CodeConverter = CodeConverter { it }
+        public val Empty: CodeWithConverter<CodeConverter> = CodeWithConverter(EmptyDeclarations, EmptyConverter)
     }
 
     val hasDeclarations: Boolean get() = declarations.isNotBlank()
@@ -27,3 +32,19 @@ public data class CodeWithConverter(val declarations: Code, val converter: (Vari
         else -> declarations + "\n" + converter(name)
     }
 }
+
+public sealed interface CodeConverter : (VariableName) -> Code
+
+public class CodeConverterImpl(private val f: (VariableName) -> Code) : CodeConverter {
+    override fun invoke(p1: VariableName): Code {
+        return f(p1)
+    }
+}
+
+public fun CodeConverter(f: (VariableName) -> Code): CodeConverter = CodeConverterImpl(f)
+
+public class ProvidedCodeConverter(public val markerName: String) : CodeConverter {
+    override fun invoke(p1: VariableName): Code {
+        return "$p1.cast<$markerName>()"
+    }
+}
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
index de874282f1..fc67c23ff2 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
@@ -4,7 +4,7 @@ import org.jetbrains.kotlinx.dataframe.impl.codeGen.ExtensionsCodeGeneratorImpl
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ShortNames
 
 public interface ExtensionsCodeGenerator {
-    public fun generate(marker: IsolatedMarker): CodeWithConverter
+    public fun generate(marker: IsolatedMarker): CodeWithConverter<*>
 
     public companion object {
         public fun create(): ExtensionsCodeGenerator = ExtensionsCodeGeneratorImpl(ShortNames)
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
index 63ceb4ffd5..001c48f65e 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
@@ -2,6 +2,7 @@ package org.jetbrains.dataframe.impl.codeGen
 
 import org.jetbrains.kotlinx.dataframe.AnyFrame
 import org.jetbrains.kotlinx.dataframe.AnyRow
+import org.jetbrains.kotlinx.dataframe.api.GroupBy
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ReplCodeGeneratorImpl
 import org.jetbrains.kotlinx.jupyter.api.Code
@@ -13,15 +14,17 @@ internal interface ReplCodeGenerator {
     fun process(
         df: AnyFrame,
         property: KProperty<*>? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<*>
 
     fun process(
         row: AnyRow,
         property: KProperty<*>? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<*>
 
     fun process(markerClass: KClass<*>): Code
 
+    fun process(groupBy: GroupBy<*, *>): CodeWithConverter<*>
+
     companion object {
         fun create(): ReplCodeGenerator = ReplCodeGeneratorImpl()
     }
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
index 73baaf8f01..c7729f26e8 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
@@ -27,6 +27,7 @@ import org.jetbrains.kotlinx.dataframe.codeGen.IsolatedMarker
 import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.NameNormalizer
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.SchemaProcessor
 import org.jetbrains.kotlinx.dataframe.codeGen.ValidFieldName
 import org.jetbrains.kotlinx.dataframe.codeGen.toNullable
@@ -43,7 +44,7 @@ internal fun Iterable<Marker>.filterRequiredForSchema(schema: DataFrameSchema) =
 internal val charsToQuote = """[ `(){}\[\].<>'"/|\\!?@:;%^&*#$-]""".toRegex()
 
 internal fun createCodeWithConverter(code: String, markerName: String) =
-    CodeWithConverter(code) { "$it.cast<$markerName>()" }
+    CodeWithConverter(code, ProvidedCodeConverter(markerName))
 
 private val letterCategories = setOf(
     CharCategory.UPPERCASE_LETTER,
@@ -345,7 +346,7 @@ internal open class ExtensionsCodeGeneratorImpl(
         return declarations.joinToString("\n")
     }
 
-    override fun generate(marker: IsolatedMarker): CodeWithConverter {
+    override fun generate(marker: IsolatedMarker): CodeWithConverter<*> {
         val code = generateExtensionProperties(marker)
         return createCodeWithConverter(code, marker.name)
     }
@@ -370,7 +371,7 @@ internal class CodeGeneratorImpl(typeRendering: TypeRenderingStrategy = FullyQua
         interfaceMode: InterfaceGenerationMode,
         extensionProperties: Boolean,
         readDfMethod: DefaultReadDfMethod?,
-    ): CodeWithConverter {
+    ): CodeWithConverter<ProvidedCodeConverter> {
         val code = when (interfaceMode) {
             NoFields, WithFields ->
                 generateInterface(
@@ -505,7 +506,7 @@ internal class CodeGeneratorImpl(typeRendering: TypeRenderingStrategy = FullyQua
     }
 }
 
-public fun CodeWithConverter.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
+public fun CodeWithConverter<*>.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
     declarations.toStandaloneSnippet(packageName, additionalImports)
 
 public fun Code.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
index ee32c8e231..ea31d88e84 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
@@ -8,11 +8,14 @@ import org.jetbrains.kotlinx.dataframe.AnyRow
 import org.jetbrains.kotlinx.dataframe.DataFrame
 import org.jetbrains.kotlinx.dataframe.DataRow
 import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
+import org.jetbrains.kotlinx.dataframe.api.GroupBy
 import org.jetbrains.kotlinx.dataframe.api.schema
+import org.jetbrains.kotlinx.dataframe.codeGen.CodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkersExtractor
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.schema.DataFrameSchema
 import org.jetbrains.kotlinx.jupyter.api.Code
 import kotlin.reflect.KClass
@@ -44,9 +47,9 @@ internal class ReplCodeGeneratorImpl : ReplCodeGenerator {
             else -> null
         }
 
-    override fun process(row: AnyRow, property: KProperty<*>?): CodeWithConverter = process(row.df(), property)
+    override fun process(row: AnyRow, property: KProperty<*>?): CodeWithConverter<*> = process(row.df(), property)
 
-    override fun process(df: AnyFrame, property: KProperty<*>?): CodeWithConverter {
+    override fun process(df: AnyFrame, property: KProperty<*>?): CodeWithConverter<*> {
         var targetSchema = df.schema()
 
         if (property != null) {
@@ -78,11 +81,21 @@ internal class ReplCodeGeneratorImpl : ReplCodeGenerator {
         return generate(schema = targetSchema, name = markerInterfacePrefix, isOpen = true)
     }
 
+    override fun process(groupBy: GroupBy<*, *>): CodeWithConverter<*> {
+        val key = generate(groupBy.keys.schema(), markerInterfacePrefix + "Keys", isOpen = false)
+        val group = generate(groupBy.groups.schema.value, markerInterfacePrefix + "Groups", isOpen = false)
+
+        return CodeWithConverter(
+            key.declarations.plus("\n").plus(group.declarations),
+            converter = CodeConverter { "$it.cast<${key.converter.markerName}, ${group.converter.markerName}>()" }
+        )
+    }
+
     fun generate(
         schema: DataFrameSchema,
         name: String,
         isOpen: Boolean,
-    ): CodeWithConverter {
+    ): CodeWithConverter<ProvidedCodeConverter> {
         val result = generator.generate(
             schema = schema,
             name = name,
diff --git a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
index af4ebd902d..4a937ff80f 100644
--- a/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
+++ b/core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
@@ -33,6 +33,7 @@ import org.jetbrains.kotlinx.dataframe.api.asDataFrame
 import org.jetbrains.kotlinx.dataframe.api.columnsCount
 import org.jetbrains.kotlinx.dataframe.api.isColumnGroup
 import org.jetbrains.kotlinx.dataframe.api.name
+import org.jetbrains.kotlinx.dataframe.codeGen.CodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.columns.ColumnGroup
 import org.jetbrains.kotlinx.dataframe.columns.ColumnReference
@@ -64,7 +65,7 @@ internal class Integration(
 
     val version = options["v"]
 
-    private fun KotlinKernelHost.execute(codeWithConverter: CodeWithConverter, argument: String): VariableName? {
+    private fun KotlinKernelHost.execute(codeWithConverter: CodeWithConverter<*>, argument: String): VariableName? {
         val code = codeWithConverter.with(argument)
         return if (code.isNotBlank()) {
             val result = execute(code)
@@ -75,7 +76,7 @@ internal class Integration(
     }
 
     private fun KotlinKernelHost.execute(
-        codeWithConverter: CodeWithConverter,
+        codeWithConverter: CodeWithConverter<*>,
         property: KProperty<*>,
         type: KType,
     ): VariableName? {
@@ -148,7 +149,7 @@ internal class Integration(
         codeGen: ReplCodeGenerator,
     ): VariableName? = if (col.isColumnGroup()) {
         val codeWithConverter = codeGen.process(col.asColumnGroup().asDataFrame(), property).let { c ->
-            CodeWithConverter(c.declarations) { c.converter("$it.asColumnGroup()") }
+            CodeWithConverter(c.declarations, converter = CodeConverter { c.converter("$it.asColumnGroup()") })
         }
         execute(
             codeWithConverter = codeWithConverter,
@@ -282,6 +283,7 @@ internal class Integration(
                     is AnyRow -> updateAnyRowVariable(instance, property, codeGen)
                     is AnyFrame -> updateAnyFrameVariable(instance, property, codeGen)
                     is ImportDataSchema -> updateImportDataSchemaVariable(instance, property)
+                    is GroupBy<*, *> -> execute(codeGen.process(instance), property, GroupBy::class.createStarProjectedType(false))
                     else -> error("${instance::class} should not be handled by Dataframe field handler")
                 }
             }
@@ -290,7 +292,8 @@ internal class Integration(
                     value is ColumnGroup<*> ||
                     value is AnyRow ||
                     value is AnyFrame ||
-                    value is ImportDataSchema
+                    value is ImportDataSchema ||
+                    value is GroupBy<*, *>
             }
         })
 
diff --git a/core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt b/core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
index a7f1d28e1c..47fc06fb49 100644
--- a/core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
+++ b/core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
@@ -52,6 +52,22 @@ class CodeGenerationTests : DataFrameJupyterTest() {
         """.checkCompilation()
     }
 
+    @Test
+    fun `groupBy`() {
+        """
+            val groupBy = dataFrameOf("a")("1", "11", "2", "22").groupBy { expr { "a"<String>().length } named "k" }
+            groupBy.keys.k
+        """.checkCompilation()
+    }
+
+    @Test
+    fun `groupBy add`() {
+        """
+            val groupBy = dataFrameOf("a")("1", "11", "2", "22").groupBy { expr { "a"<String>().length } named "k" }.add("newCol") { 42 }
+            groupBy.aggregate { newCol into "newCol" }
+        """.checkCompilation()
+    }
+
     @Test
     fun `interface without body compiled correctly`() {
         """
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
index 4d0245b159..378612717c 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/cast.kt
@@ -33,6 +33,8 @@ else cast()
 
 public fun <T> AnyRow.cast(): DataRow<T> = this as DataRow<T>
 
+public fun <T, G> GroupBy<*, *>.cast(): GroupBy<T, G> = this as GroupBy<T, G>
+
 public inline fun <reified T> AnyRow.cast(verify: Boolean = true): DataRow<T> = df().cast<T>(verify)[0]
 
 public fun <T> AnyCol.cast(): DataColumn<T> = this as DataColumn<T>
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
index 4ec4202584..a34545fe16 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerator.kt
@@ -7,6 +7,7 @@ import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkersExtractor
 import org.jetbrains.kotlinx.dataframe.codeGen.NameNormalizer
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.CodeGeneratorImpl
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.FullyQualifiedNames
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ShortNames
@@ -22,7 +23,7 @@ public enum class InterfaceGenerationMode {
     None;
 }
 
-public data class CodeGenResult(val code: CodeWithConverter, val newMarkers: List<Marker>)
+public data class CodeGenResult(val code: CodeWithConverter<ProvidedCodeConverter>, val newMarkers: List<Marker>)
 
 public interface CodeGenerator : ExtensionsCodeGenerator {
 
@@ -43,7 +44,7 @@ public interface CodeGenerator : ExtensionsCodeGenerator {
         interfaceMode: InterfaceGenerationMode,
         extensionProperties: Boolean,
         readDfMethod: DefaultReadDfMethod? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<ProvidedCodeConverter>
 
     public companion object {
         public fun create(useFqNames: Boolean = true): CodeGenerator {
@@ -61,7 +62,7 @@ internal fun CodeGenerator.generate(
     markerClass: KClass<*>,
     interfaceMode: InterfaceGenerationMode,
     extensionProperties: Boolean,
-): CodeWithConverter = generate(
+): CodeWithConverter<ProvidedCodeConverter> = generate(
     MarkersExtractor.get(markerClass),
     interfaceMode,
     extensionProperties
@@ -70,4 +71,4 @@ internal fun CodeGenerator.generate(
 public inline fun <reified T> CodeGenerator.generate(
     interfaceMode: InterfaceGenerationMode,
     extensionProperties: Boolean,
-): CodeWithConverter = generate(T::class, interfaceMode, extensionProperties)
+): CodeWithConverter<ProvidedCodeConverter> = generate(T::class, interfaceMode, extensionProperties)
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
index dd48b739f4..9bbe416142 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeWithConverter.kt
@@ -7,14 +7,19 @@ import org.jetbrains.kotlinx.jupyter.api.VariableName
  * Class representing generated code declarations for a [Marker].
  *
  * @param declarations The generated code.
+ * @param converter Needs to provide additional info (name) from org.jetbrains.dataframe.impl.codeGen.CodeGenerator to its callers
+ * But at the same time name doesn't make sense for GroupBy where code to be executed contains two declarations
  * @param converter Optional converter for the [Marker], such as a [org.jetbrains.kotlinx.dataframe.api.cast], often used for Jupyter.
  */
-public data class CodeWithConverter(val declarations: Code, val converter: (VariableName) -> Code = EmptyConverter) {
+public data class CodeWithConverter<T : CodeConverter>(
+    val declarations: Code,
+    val converter: T
+) {
 
     public companion object {
         public const val EmptyDeclarations: Code = ""
-        public val EmptyConverter: (VariableName) -> Code = { it }
-        public val Empty: CodeWithConverter = CodeWithConverter(EmptyDeclarations, EmptyConverter)
+        public val EmptyConverter: CodeConverter = CodeConverter { it }
+        public val Empty: CodeWithConverter<CodeConverter> = CodeWithConverter(EmptyDeclarations, EmptyConverter)
     }
 
     val hasDeclarations: Boolean get() = declarations.isNotBlank()
@@ -27,3 +32,19 @@ public data class CodeWithConverter(val declarations: Code, val converter: (Vari
         else -> declarations + "\n" + converter(name)
     }
 }
+
+public sealed interface CodeConverter : (VariableName) -> Code
+
+public class CodeConverterImpl(private val f: (VariableName) -> Code) : CodeConverter {
+    override fun invoke(p1: VariableName): Code {
+        return f(p1)
+    }
+}
+
+public fun CodeConverter(f: (VariableName) -> Code): CodeConverter = CodeConverterImpl(f)
+
+public class ProvidedCodeConverter(public val markerName: String) : CodeConverter {
+    override fun invoke(p1: VariableName): Code {
+        return "$p1.cast<$markerName>()"
+    }
+}
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
index de874282f1..fc67c23ff2 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ExtensionsCodeGenerator.kt
@@ -4,7 +4,7 @@ import org.jetbrains.kotlinx.dataframe.impl.codeGen.ExtensionsCodeGeneratorImpl
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ShortNames
 
 public interface ExtensionsCodeGenerator {
-    public fun generate(marker: IsolatedMarker): CodeWithConverter
+    public fun generate(marker: IsolatedMarker): CodeWithConverter<*>
 
     public companion object {
         public fun create(): ExtensionsCodeGenerator = ExtensionsCodeGeneratorImpl(ShortNames)
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
index 63ceb4ffd5..001c48f65e 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenerator.kt
@@ -2,6 +2,7 @@ package org.jetbrains.dataframe.impl.codeGen
 
 import org.jetbrains.kotlinx.dataframe.AnyFrame
 import org.jetbrains.kotlinx.dataframe.AnyRow
+import org.jetbrains.kotlinx.dataframe.api.GroupBy
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.impl.codeGen.ReplCodeGeneratorImpl
 import org.jetbrains.kotlinx.jupyter.api.Code
@@ -13,15 +14,17 @@ internal interface ReplCodeGenerator {
     fun process(
         df: AnyFrame,
         property: KProperty<*>? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<*>
 
     fun process(
         row: AnyRow,
         property: KProperty<*>? = null,
-    ): CodeWithConverter
+    ): CodeWithConverter<*>
 
     fun process(markerClass: KClass<*>): Code
 
+    fun process(groupBy: GroupBy<*, *>): CodeWithConverter<*>
+
     companion object {
         fun create(): ReplCodeGenerator = ReplCodeGeneratorImpl()
     }
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
index 73baaf8f01..c7729f26e8 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/CodeGeneratorImpl.kt
@@ -27,6 +27,7 @@ import org.jetbrains.kotlinx.dataframe.codeGen.IsolatedMarker
 import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.NameNormalizer
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.SchemaProcessor
 import org.jetbrains.kotlinx.dataframe.codeGen.ValidFieldName
 import org.jetbrains.kotlinx.dataframe.codeGen.toNullable
@@ -43,7 +44,7 @@ internal fun Iterable<Marker>.filterRequiredForSchema(schema: DataFrameSchema) =
 internal val charsToQuote = """[ `(){}\[\].<>'"/|\\!?@:;%^&*#$-]""".toRegex()
 
 internal fun createCodeWithConverter(code: String, markerName: String) =
-    CodeWithConverter(code) { "$it.cast<$markerName>()" }
+    CodeWithConverter(code, ProvidedCodeConverter(markerName))
 
 private val letterCategories = setOf(
     CharCategory.UPPERCASE_LETTER,
@@ -345,7 +346,7 @@ internal open class ExtensionsCodeGeneratorImpl(
         return declarations.joinToString("\n")
     }
 
-    override fun generate(marker: IsolatedMarker): CodeWithConverter {
+    override fun generate(marker: IsolatedMarker): CodeWithConverter<*> {
         val code = generateExtensionProperties(marker)
         return createCodeWithConverter(code, marker.name)
     }
@@ -370,7 +371,7 @@ internal class CodeGeneratorImpl(typeRendering: TypeRenderingStrategy = FullyQua
         interfaceMode: InterfaceGenerationMode,
         extensionProperties: Boolean,
         readDfMethod: DefaultReadDfMethod?,
-    ): CodeWithConverter {
+    ): CodeWithConverter<ProvidedCodeConverter> {
         val code = when (interfaceMode) {
             NoFields, WithFields ->
                 generateInterface(
@@ -505,7 +506,7 @@ internal class CodeGeneratorImpl(typeRendering: TypeRenderingStrategy = FullyQua
     }
 }
 
-public fun CodeWithConverter.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
+public fun CodeWithConverter<*>.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
     declarations.toStandaloneSnippet(packageName, additionalImports)
 
 public fun Code.toStandaloneSnippet(packageName: String, additionalImports: List<String>): String =
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
index ee32c8e231..ea31d88e84 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/ReplCodeGeneratorImpl.kt
@@ -8,11 +8,14 @@ import org.jetbrains.kotlinx.dataframe.AnyRow
 import org.jetbrains.kotlinx.dataframe.DataFrame
 import org.jetbrains.kotlinx.dataframe.DataRow
 import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
+import org.jetbrains.kotlinx.dataframe.api.GroupBy
 import org.jetbrains.kotlinx.dataframe.api.schema
+import org.jetbrains.kotlinx.dataframe.codeGen.CodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.Marker
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkerVisibility
 import org.jetbrains.kotlinx.dataframe.codeGen.MarkersExtractor
+import org.jetbrains.kotlinx.dataframe.codeGen.ProvidedCodeConverter
 import org.jetbrains.kotlinx.dataframe.schema.DataFrameSchema
 import org.jetbrains.kotlinx.jupyter.api.Code
 import kotlin.reflect.KClass
@@ -44,9 +47,9 @@ internal class ReplCodeGeneratorImpl : ReplCodeGenerator {
             else -> null
         }
 
-    override fun process(row: AnyRow, property: KProperty<*>?): CodeWithConverter = process(row.df(), property)
+    override fun process(row: AnyRow, property: KProperty<*>?): CodeWithConverter<*> = process(row.df(), property)
 
-    override fun process(df: AnyFrame, property: KProperty<*>?): CodeWithConverter {
+    override fun process(df: AnyFrame, property: KProperty<*>?): CodeWithConverter<*> {
         var targetSchema = df.schema()
 
         if (property != null) {
@@ -78,11 +81,21 @@ internal class ReplCodeGeneratorImpl : ReplCodeGenerator {
         return generate(schema = targetSchema, name = markerInterfacePrefix, isOpen = true)
     }
 
+    override fun process(groupBy: GroupBy<*, *>): CodeWithConverter<*> {
+        val key = generate(groupBy.keys.schema(), markerInterfacePrefix + "Keys", isOpen = false)
+        val group = generate(groupBy.groups.schema.value, markerInterfacePrefix + "Groups", isOpen = false)
+
+        return CodeWithConverter(
+            key.declarations.plus("\n").plus(group.declarations),
+            converter = CodeConverter { "$it.cast<${key.converter.markerName}, ${group.converter.markerName}>()" }
+        )
+    }
+
     fun generate(
         schema: DataFrameSchema,
         name: String,
         isOpen: Boolean,
-    ): CodeWithConverter {
+    ): CodeWithConverter<ProvidedCodeConverter> {
         val result = generator.generate(
             schema = schema,
             name = name,
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
index af4ebd902d..4a937ff80f 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/Integration.kt
@@ -33,6 +33,7 @@ import org.jetbrains.kotlinx.dataframe.api.asDataFrame
 import org.jetbrains.kotlinx.dataframe.api.columnsCount
 import org.jetbrains.kotlinx.dataframe.api.isColumnGroup
 import org.jetbrains.kotlinx.dataframe.api.name
+import org.jetbrains.kotlinx.dataframe.codeGen.CodeConverter
 import org.jetbrains.kotlinx.dataframe.codeGen.CodeWithConverter
 import org.jetbrains.kotlinx.dataframe.columns.ColumnGroup
 import org.jetbrains.kotlinx.dataframe.columns.ColumnReference
@@ -64,7 +65,7 @@ internal class Integration(
 
     val version = options["v"]
 
-    private fun KotlinKernelHost.execute(codeWithConverter: CodeWithConverter, argument: String): VariableName? {
+    private fun KotlinKernelHost.execute(codeWithConverter: CodeWithConverter<*>, argument: String): VariableName? {
         val code = codeWithConverter.with(argument)
         return if (code.isNotBlank()) {
             val result = execute(code)
@@ -75,7 +76,7 @@ internal class Integration(
     }
 
     private fun KotlinKernelHost.execute(
-        codeWithConverter: CodeWithConverter,
+        codeWithConverter: CodeWithConverter<*>,
         property: KProperty<*>,
         type: KType,
     ): VariableName? {
@@ -148,7 +149,7 @@ internal class Integration(
         codeGen: ReplCodeGenerator,
     ): VariableName? = if (col.isColumnGroup()) {
         val codeWithConverter = codeGen.process(col.asColumnGroup().asDataFrame(), property).let { c ->
-            CodeWithConverter(c.declarations) { c.converter("$it.asColumnGroup()") }
+            CodeWithConverter(c.declarations, converter = CodeConverter { c.converter("$it.asColumnGroup()") })
         }
         execute(
             codeWithConverter = codeWithConverter,
@@ -282,6 +283,7 @@ internal class Integration(
                     is AnyRow -> updateAnyRowVariable(instance, property, codeGen)
                     is AnyFrame -> updateAnyFrameVariable(instance, property, codeGen)
                     is ImportDataSchema -> updateImportDataSchemaVariable(instance, property)
+                    is GroupBy<*, *> -> execute(codeGen.process(instance), property, GroupBy::class.createStarProjectedType(false))
                     else -> error("${instance::class} should not be handled by Dataframe field handler")
                 }
             }
@@ -290,7 +292,8 @@ internal class Integration(
                     value is ColumnGroup<*> ||
                     value is AnyRow ||
                     value is AnyFrame ||
-                    value is ImportDataSchema
+                    value is ImportDataSchema ||
+                    value is GroupBy<*, *>
             }
         })
 
diff --git a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
index a7f1d28e1c..47fc06fb49 100644
--- a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
+++ b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
@@ -52,6 +52,22 @@ class CodeGenerationTests : DataFrameJupyterTest() {
         """.checkCompilation()
     }
 
+    @Test
+    fun `groupBy`() {
+        """
+            val groupBy = dataFrameOf("a")("1", "11", "2", "22").groupBy { expr { "a"<String>().length } named "k" }
+            groupBy.keys.k
+        """.checkCompilation()
+    }
+
+    @Test
+    fun `groupBy add`() {
+        """
+            val groupBy = dataFrameOf("a")("1", "11", "2", "22").groupBy { expr { "a"<String>().length } named "k" }.add("newCol") { 42 }
+            groupBy.aggregate { newCol into "newCol" }
+        """.checkCompilation()
+    }
+
     @Test
     fun `interface without body compiled correctly`() {
         """