diff --git a/src/protean/core/aggregate.py b/src/protean/core/aggregate.py
index 677583eb..7425860c 100644
--- a/src/protean/core/aggregate.py
+++ b/src/protean/core/aggregate.py
@@ -58,13 +58,14 @@ def __init__(self, *args, **kwargs):
     @classmethod
     def _default_options(cls):
         return [
-            ("auto_add_id_field", True),
-            ("provider", "default"),
+            ("abstract", False),
             ("aggregate_cluster", None),
+            ("auto_add_id_field", True),
+            ("fact_events", False),
             ("model", None),
-            ("stream_name", inflection.underscore(cls.__name__)),
+            ("provider", "default"),
             ("schema_name", inflection.underscore(cls.__name__)),
-            ("fact_events", False),
+            ("stream_name", inflection.underscore(cls.__name__)),
         ]
 
 
diff --git a/src/protean/core/command.py b/src/protean/core/command.py
index 1beb8263..e846e566 100644
--- a/src/protean/core/command.py
+++ b/src/protean/core/command.py
@@ -52,9 +52,9 @@ def __setattr__(self, name, value):
     def _default_options(cls):
         return [
             ("abstract", False),
+            ("aggregate_cluster", None),
             ("part_of", None),
             ("stream_name", None),
-            ("aggregate_cluster", None),
         ]
 
     @classmethod
diff --git a/src/protean/core/entity.py b/src/protean/core/entity.py
index c9b4cfa2..7f4a86af 100644
--- a/src/protean/core/entity.py
+++ b/src/protean/core/entity.py
@@ -119,10 +119,11 @@ def __init_subclass__(subclass) -> None:
     @classmethod
     def _default_options(cls):
         return [
+            ("aggregate_cluster", None),
             ("auto_add_id_field", True),
             ("model", None),
             ("part_of", None),
-            ("aggregate_cluster", None),
+            ("provider", "default"),
             ("schema_name", inflection.underscore(cls.__name__)),
         ]
 
diff --git a/src/protean/core/event.py b/src/protean/core/event.py
index 83501c29..87facd5a 100644
--- a/src/protean/core/event.py
+++ b/src/protean/core/event.py
@@ -87,9 +87,9 @@ def _default_options(cls):
 
         return [
             ("abstract", False),
+            ("aggregate_cluster", None),
             ("part_of", None),
             ("stream_name", part_of.meta_.stream_name if part_of else None),
-            ("aggregate_cluster", None),
         ]
 
     @classmethod
diff --git a/src/protean/core/event_handler.py b/src/protean/core/event_handler.py
index f4366a45..c85e0b18 100644
--- a/src/protean/core/event_handler.py
+++ b/src/protean/core/event_handler.py
@@ -27,8 +27,8 @@ def _default_options(cls):
 
         return [
             ("part_of", None),
-            ("stream_name", part_of.meta_.stream_name if part_of else None),
             ("source_stream", None),
+            ("stream_name", part_of.meta_.stream_name if part_of else None),
         ]
 
 
diff --git a/src/protean/core/event_sourced_aggregate.py b/src/protean/core/event_sourced_aggregate.py
index 762c7a6f..7dca00a6 100644
--- a/src/protean/core/event_sourced_aggregate.py
+++ b/src/protean/core/event_sourced_aggregate.py
@@ -41,9 +41,10 @@ def __new__(cls, *args, **kwargs):
     @classmethod
     def _default_options(cls):
         return [
+            ("aggregate_cluster", None),
             ("auto_add_id_field", True),
+            ("fact_events", False),
             ("stream_name", inflection.underscore(cls.__name__)),
-            ("aggregate_cluster", None),
         ]
 
     def __init_subclass__(subclass) -> None:
diff --git a/src/protean/core/event_sourced_repository.py b/src/protean/core/event_sourced_repository.py
index 5a5263cc..e64aff45 100644
--- a/src/protean/core/event_sourced_repository.py
+++ b/src/protean/core/event_sourced_repository.py
@@ -36,21 +36,32 @@ def add(self, aggregate: BaseEventSourcedAggregate) -> None:
                 {"_entity": ["Aggregate object to persist is invalid"]}
             )
 
-        # `add` is typically invoked in handler methods in Command Handlers and Event Handlers, which are
-        #   enclosed in a UoW automatically. Therefore, if there is a UoW in progress, we can assume
-        #   that it is the active session. If not, we will start a new UoW and commit it after the operation
-        #   is complete.
-        own_current_uow = None
-        if not (current_uow and current_uow.in_progress):
-            own_current_uow = UnitOfWork()
-            own_current_uow.start()
-
-        uow = current_uow or own_current_uow
-        uow._add_to_identity_map(aggregate)
-
-        # If we started a UnitOfWork, commit it now
-        if own_current_uow:
-            own_current_uow.commit()
+        # Proceed only if aggregate has events
+        if len(aggregate._events) > 0:
+            # `add` is typically invoked in handler methods in Command Handlers and Event Handlers, which are
+            #   enclosed in a UoW automatically. Therefore, if there is a UoW in progress, we can assume
+            #   that it is the active session. If not, we will start a new UoW and commit it after the operation
+            #   is complete.
+            own_current_uow = None
+            if not (current_uow and current_uow.in_progress):
+                own_current_uow = UnitOfWork()
+                own_current_uow.start()
+
+            uow = current_uow or own_current_uow
+
+            # If Aggregate has signed up Fact Events, raise them now
+            if aggregate.meta_.fact_events:
+                payload = aggregate.to_dict()
+
+                # Construct and raise the Fact Event
+                fact_event = aggregate._fact_event_cls(**payload)
+                aggregate.raise_(fact_event)
+
+            uow._add_to_identity_map(aggregate)
+
+            # If we started a UnitOfWork, commit it now
+            if own_current_uow:
+                own_current_uow.commit()
 
     def get(self, identifier: Identifier) -> BaseEventSourcedAggregate:
         """Retrieve a fully-formed Aggregate from a stream of Events.
diff --git a/src/protean/core/model.py b/src/protean/core/model.py
index 49c61794..3fcbb7f3 100644
--- a/src/protean/core/model.py
+++ b/src/protean/core/model.py
@@ -20,9 +20,9 @@ def __new__(cls, *args, **kwargs):
     @classmethod
     def _default_options(cls):
         return [
+            ("database", None),
             ("entity_cls", None),
             ("schema_name", None),
-            ("database", None),
         ]
 
     @classmethod
diff --git a/src/protean/core/repository.py b/src/protean/core/repository.py
index a63cb261..53efef87 100644
--- a/src/protean/core/repository.py
+++ b/src/protean/core/repository.py
@@ -42,7 +42,7 @@ class BaseRepository(Element, OptionsMixin):
 
     @classmethod
     def _default_options(cls):
-        return [("part_of", None), ("database", "ALL")]
+        return [("database", "ALL"), ("part_of", None)]
 
     def __new__(cls, *args, **kwargs):
         # Prevent instantiation of `BaseRepository itself`
@@ -133,7 +133,7 @@ def add(self, aggregate: BaseAggregate) -> BaseAggregate:  # noqa: C901
         ):
             self._dao.save(aggregate)
 
-            # If there are Fact Events associated with the Aggregate, raise them now
+            # If Aggregate has signed up Fact Events, raise them now
             if aggregate.meta_.fact_events:
                 payload = aggregate.to_dict()
 
diff --git a/src/protean/core/serializer.py b/src/protean/core/serializer.py
index 8b54f9bd..b34421f3 100644
--- a/src/protean/core/serializer.py
+++ b/src/protean/core/serializer.py
@@ -195,6 +195,10 @@ def __new__(cls, *args, **kwargs):
             raise NotSupportedError("BaseSerializer cannot be instantiated")
         return super().__new__(cls)
 
+    @classmethod
+    def _default_options(cls):
+        return []
+
 
 def serializer_factory(element_cls, **kwargs):
     return derive_element_class(element_cls, BaseSerializer, **kwargs)
diff --git a/src/protean/core/subscriber.py b/src/protean/core/subscriber.py
index 9fc5f775..a7d903b9 100644
--- a/src/protean/core/subscriber.py
+++ b/src/protean/core/subscriber.py
@@ -26,7 +26,7 @@ def __new__(cls, *args, **kwargs):
 
     @classmethod
     def _default_options(cls):
-        return [("event", None), ("broker", "default")]
+        return [("broker", "default"), ("event", None)]
 
     @abstractmethod
     def __call__(self, event: BaseEvent) -> Optional[Any]:
diff --git a/src/protean/core/value_object.py b/src/protean/core/value_object.py
index 073b32a3..6681ea7b 100644
--- a/src/protean/core/value_object.py
+++ b/src/protean/core/value_object.py
@@ -21,6 +21,13 @@ def __new__(cls, *args, **kwargs):
             raise NotSupportedError("BaseValueObject cannot be instantiated")
         return super().__new__(cls)
 
+    @classmethod
+    def _default_options(cls):
+        return [
+            ("abstract", False),
+            ("part_of", None),
+        ]
+
     def __init_subclass__(subclass) -> None:
         super().__init_subclass__()
 
diff --git a/src/protean/core/view.py b/src/protean/core/view.py
index 7257b7a0..0bb4c7e9 100644
--- a/src/protean/core/view.py
+++ b/src/protean/core/view.py
@@ -24,11 +24,12 @@ def __new__(cls, *args, **kwargs):
     @classmethod
     def _default_options(cls):
         return [
-            ("provider", "default"),
+            ("abstract", False),
             ("cache", None),
             ("model", None),
-            ("schema_name", inflection.underscore(cls.__name__)),
             ("order_by", ()),
+            ("provider", "default"),
+            ("schema_name", inflection.underscore(cls.__name__)),
         ]
 
     def __init_subclass__(subclass) -> None:
diff --git a/src/protean/domain/__init__.py b/src/protean/domain/__init__.py
index 9abd109a..5423014e 100644
--- a/src/protean/domain/__init__.py
+++ b/src/protean/domain/__init__.py
@@ -21,7 +21,11 @@
 from protean.core.model import BaseModel
 from protean.core.repository import BaseRepository
 from protean.domain.registry import _DomainRegistry
-from protean.exceptions import ConfigurationError, IncorrectUsageError
+from protean.exceptions import (
+    ConfigurationError,
+    IncorrectUsageError,
+    NotSupportedError,
+)
 from protean.fields import HasMany, HasOne, Reference, ValueObject
 from protean.reflection import declared_fields, has_fields
 from protean.utils import (
@@ -561,7 +565,9 @@ def register(self, element_cls: Any, **kwargs: dict) -> Any:
         if getattr(element_cls, "element_type", None) not in [
             element for element in DomainObjects
         ]:
-            raise NotImplementedError
+            raise NotSupportedError(
+                f"Element `{element_cls.__name__}` is not a valid element class"
+            )
 
         return self._register_element(element_cls.element_type, element_cls, **kwargs)
 
@@ -786,12 +792,18 @@ def _set_aggregate_cluster_options(self):
 
     def _generate_fact_event_classes(self):
         """Generate FactEvent classes for all aggregates with `fact_events` enabled"""
-        for _, element in self.registry._elements[
-            DomainObjects.AGGREGATE.value
-        ].items():
-            if element.cls.meta_.fact_events:
-                event_cls = element_to_fact_event(element.cls)
-                self.register(event_cls, part_of=element.cls)
+        for element_type in [
+            DomainObjects.AGGREGATE,
+            DomainObjects.EVENT_SOURCED_AGGREGATE,
+        ]:
+            for _, element in self.registry._elements[element_type.value].items():
+                if element.cls.meta_.fact_events:
+                    event_cls = element_to_fact_event(element.cls)
+                    self.register(
+                        event_cls,
+                        part_of=element.cls,
+                        stream_name=element.cls.meta_.stream_name + "-fact",
+                    )
 
     ######################
     # Element Decorators #
diff --git a/src/protean/domain/registry.py b/src/protean/domain/registry.py
index ffbd108f..63dbba0b 100644
--- a/src/protean/domain/registry.py
+++ b/src/protean/domain/registry.py
@@ -5,6 +5,7 @@
 
 import inflection
 
+from protean.exceptions import NotSupportedError
 from protean.utils import DomainObjects, fully_qualified_name
 
 logger = logging.getLogger(__name__)
@@ -78,7 +79,9 @@ def _is_invalid_element_cls(self, element_cls):
 
     def register_element(self, element_cls):
         if self._is_invalid_element_cls(element_cls):
-            raise NotImplementedError
+            raise NotSupportedError(
+                f"Element `{element_cls.__name__}` is not a valid element class"
+            )
 
         element_name = fully_qualified_name(element_cls)
 
diff --git a/src/protean/utils/__init__.py b/src/protean/utils/__init__.py
index 026d3dad..ec58710b 100644
--- a/src/protean/utils/__init__.py
+++ b/src/protean/utils/__init__.py
@@ -134,6 +134,11 @@ class DomainObjects(Enum):
 def derive_element_class(element_cls, base_cls, **opts):
     from protean.container import Options
 
+    # Ensure options being passed in are known
+    known_options = [name for (name, _) in base_cls._default_options()]
+    if not all(opt in known_options for opt in opts):
+        raise ConfigurationError(f"Unknown option(s) {set(opts) - set(known_options)}")
+
     if not issubclass(element_cls, base_cls):
         try:
             new_dict = element_cls.__dict__.copy()
diff --git a/src/protean/utils/mixins.py b/src/protean/utils/mixins.py
index 41ae709b..5beaaac9 100644
--- a/src/protean/utils/mixins.py
+++ b/src/protean/utils/mixins.py
@@ -151,8 +151,11 @@ def to_aggregate_event_message(
                 **cls.derived_metadata(MessageType.EVENT.value),
                 # schema_version=event.meta_.version,  # FIXME Maintain version for event
             ),
-            # Expect the previous version
-            expected_version=int(event._metadata.sequence_id) - 1,
+            # If this is a Fact Event, don't set an expected version.
+            # Otherwise, expect the previous version
+            expected_version=None
+            if event.__class__.__name__.endswith("FactEvent")
+            else int(event._metadata.sequence_id) - 1,
         )
 
     def to_object(self) -> Union[BaseEvent, BaseCommand]:
diff --git a/tests/aggregate/events/test_raising_fact_events.py b/tests/aggregate/events/test_raising_fact_events.py
index c32a36c3..15f31fac 100644
--- a/tests/aggregate/events/test_raising_fact_events.py
+++ b/tests/aggregate/events/test_raising_fact_events.py
@@ -29,7 +29,7 @@ def test_generation_of_first_fact_event_on_persistence(test_domain):
     test_domain.repository_for(User).add(user)
 
     # Read event from event store
-    event_messages = test_domain.event_store.store.read(f"user-{user.id}")
+    event_messages = test_domain.event_store.store.read(f"user-fact-{user.id}")
     assert len(event_messages) == 1
 
     # Deserialize event
diff --git a/tests/domain/tests.py b/tests/domain/tests.py
index 1feb1902..b77210e1 100644
--- a/tests/domain/tests.py
+++ b/tests/domain/tests.py
@@ -1,7 +1,11 @@
 import pytest
 
 from protean import BaseAggregate, BaseEntity, Domain
-from protean.exceptions import ConfigurationError, IncorrectUsageError
+from protean.exceptions import (
+    ConfigurationError,
+    IncorrectUsageError,
+    NotSupportedError,
+)
 from protean.fields import DateTime, HasMany, HasOne, Reference, String, Text
 from protean.reflection import declared_fields
 from protean.utils import fully_qualified_name
@@ -9,11 +13,13 @@
 from .elements import UserAggregate, UserEntity, UserFoo, UserVO
 
 
-class TestDomainRegistration:
+class TestElementRegistration:
     def test_that_only_recognized_element_types_can_be_registered(self, test_domain):
-        with pytest.raises(NotImplementedError):
+        with pytest.raises(NotSupportedError) as exc:
             test_domain.registry.register_element(UserFoo)
 
+        assert exc.value.args[0] == "Element `UserFoo` is not a valid element class"
+
     def test_register_aggregate_with_domain(self, test_domain):
         test_domain.registry.register_element(UserAggregate)
 
@@ -41,9 +47,20 @@ class Foo:
         class Bar(Foo):
             foo = String(max_length=50)
 
-        with pytest.raises(NotImplementedError):
+        with pytest.raises(NotSupportedError) as exc:
             test_domain.register(Bar)
 
+        assert exc.value.args[0] == "Element `Bar` is not a valid element class"
+
+    def test_options_are_validated_on_element_registration(self, test_domain):
+        class Foo(BaseAggregate):
+            foo = String(max_length=50)
+
+        with pytest.raises(ConfigurationError) as exc:
+            test_domain.register(Foo, foo="bar")
+
+        assert exc.value.args[0] == "Unknown option(s) {'foo'}"
+
 
 class TestDomainAnnotations:
     # Individual test cases for registering domain elements with
diff --git a/tests/event_sourced_aggregates/events/test_fact_event_generation.py b/tests/event_sourced_aggregates/events/test_fact_event_generation.py
new file mode 100644
index 00000000..32ca7a02
--- /dev/null
+++ b/tests/event_sourced_aggregates/events/test_fact_event_generation.py
@@ -0,0 +1,103 @@
+import pytest
+
+from protean import BaseEvent, BaseEventSourcedAggregate, apply
+from protean.fields import Identifier, String
+from protean.utils.mixins import Message
+
+
+class Registered(BaseEvent):
+    id = Identifier()
+    email = String()
+    name = String()
+
+
+class Renamed(BaseEvent):
+    id = Identifier()
+    name = String()
+
+
+class User(BaseEventSourcedAggregate):
+    email = String()
+    name = String()
+
+    @apply
+    def registered(self, event: Registered) -> None:
+        self.email = event.email
+        self.name = event.name
+
+    @apply
+    def renamed(self, event: Renamed) -> None:
+        self.name = event.name
+
+
+@pytest.fixture(autouse=True)
+def register_elements(test_domain):
+    test_domain.register(User, fact_events=True)
+    test_domain.register(Registered, part_of=User)
+    test_domain.register(Renamed, part_of=User)
+    test_domain.init(traverse=False)
+
+
+def test_event_sourced_aggregate_can_be_marked_for_fact_event_generation(test_domain):
+    assert User.meta_.fact_events is True
+
+
+def test_generation_of_first_fact_event_on_persistence(test_domain):
+    user = User(name="John Doe", email="john.doe@example.com")
+    user.raise_(Registered(id=user.id, email=user.email, name=user.name))
+
+    test_domain.repository_for(User).add(user)
+
+    # Read event from event store
+    event_messages = test_domain.event_store.store.read(f"user-{user.id}")
+    assert len(event_messages) == 1
+
+    # Read fact events from event store
+    fact_event_messages = test_domain.event_store.store.read(f"user-fact-{user.id}")
+    assert len(fact_event_messages) == 1
+
+    # Deserialize event
+    event = Message.to_object(fact_event_messages[0])
+    assert event is not None
+    assert event.__class__.__name__ == "UserFactEvent"
+    assert event.name == "John Doe"
+    assert event.email == "john.doe@example.com"
+
+
+def test_generation_of_subsequent_fact_events_after_fetch(test_domain):
+    # Initialize and save
+    user = User(name="John Doe", email="john.doe@example.com")
+    user.raise_(Registered(id=user.id, email=user.email, name=user.name))
+
+    # Persist the user
+    test_domain.repository_for(User).add(user)
+
+    # Fetch the aggregate
+    refreshed_user = test_domain.repository_for(User).get(user.id)
+
+    # Simulate a name update
+    refreshed_user.name = "Jane Doe"
+    refreshed_user.raise_(Renamed(id=refreshed_user.id, name="Jane Doe"))
+
+    # Store the updated user
+    test_domain.repository_for(User).add(refreshed_user)
+
+    # Read event from event store
+    event_messages = test_domain.event_store.store.read(f"user-{user.id}")
+    assert len(event_messages) == 2
+
+    # Read fact events from event store
+    fact_event_messages = test_domain.event_store.store.read(f"user-fact-{user.id}")
+    assert len(fact_event_messages) == 2
+
+    # Deserialize 1st event
+    event = Message.to_object(fact_event_messages[0])
+    assert event is not None
+    assert event.__class__.__name__ == "UserFactEvent"
+    assert event.name == "John Doe"
+
+    # Deserialize 2nd event
+    event = Message.to_object(fact_event_messages[1])
+    assert event is not None
+    assert event.__class__.__name__ == "UserFactEvent"
+    assert event.name == "Jane Doe"
diff --git a/tests/event_sourced_repository/test_add_uow.py b/tests/event_sourced_repository/test_add_uow.py
index 48945763..d2902779 100644
--- a/tests/event_sourced_repository/test_add_uow.py
+++ b/tests/event_sourced_repository/test_add_uow.py
@@ -1,7 +1,7 @@
 import mock
 import pytest
 
-from protean import BaseEventSourcedAggregate
+from protean import BaseEvent, BaseEventSourcedAggregate
 from protean.fields import Identifier, String
 
 
@@ -11,6 +11,12 @@ class User(BaseEventSourcedAggregate):
     name = String()
 
 
+class Registered(BaseEvent):
+    id = Identifier()
+    email = String()
+    name = String()
+
+
 @pytest.fixture(autouse=True)
 def register_elements(test_domain):
     test_domain.register(User)
@@ -27,6 +33,7 @@ def test_that_method_is_enclosed_in_uow(mock_commit, mock_start, test_domain):
 
     with test_domain.domain_context():
         user = User(id=1, email="john.doe@example.com", name="John Doe")
+        user.raise_(Registered(id=1, email="john.doe@example.com", name="John Doe"))
         test_domain.repository_for(User).add(user)
 
     mock_parent.assert_has_calls(
diff --git a/tests/test_registry.py b/tests/test_registry.py
index 409aa402..8ab8c5ba 100644
--- a/tests/test_registry.py
+++ b/tests/test_registry.py
@@ -6,6 +6,7 @@
 
 from protean import BaseAggregate, BaseEntity
 from protean.domain.registry import _DomainRegistry
+from protean.exceptions import NotSupportedError
 from protean.fields import DateTime, Identifier, Integer, String
 from protean.utils import DomainObjects
 
@@ -78,13 +79,13 @@ class FooBar3:
 
     register = _DomainRegistry()
 
-    with pytest.raises(NotImplementedError):
+    with pytest.raises(NotSupportedError):
         register.register_element(FooBar1)
 
-    with pytest.raises(NotImplementedError):
+    with pytest.raises(NotSupportedError):
         register.register_element(FooBar2)
 
-    with pytest.raises(NotImplementedError):
+    with pytest.raises(NotSupportedError):
         register.register_element(FooBar3)
 
 
diff --git a/tests/value_object/test_vo_in_vo.py b/tests/value_object/test_vo_in_vo.py
new file mode 100644
index 00000000..5b8940be
--- /dev/null
+++ b/tests/value_object/test_vo_in_vo.py
@@ -0,0 +1,42 @@
+import pytest
+
+from protean import BaseValueObject
+from protean.fields import String, ValueObject
+from protean.reflection import fields
+
+
+class Address(BaseValueObject):
+    street = String(max_length=50)
+    city = String(max_length=25)
+    state = String(max_length=25)
+    zip_code = String(max_length=10)
+
+
+class Contact(BaseValueObject):
+    email = String(max_length=255)
+    phone_number = String(max_length=255)
+    address = ValueObject(Address)
+
+
+@pytest.fixture(autouse=True)
+def register_elements(test_domain):
+    test_domain.register(Contact)
+    test_domain.register(Address)
+    test_domain.init(traverse=False)
+
+
+def test_contact_has_address_vo():
+    assert isinstance(fields(Contact)["address"], ValueObject)
+    assert hasattr(Contact, "address")
+
+
+def test_outer_vo_initialization():
+    contact = Contact(
+        email="<EMAIL>",
+        phone_number="123-456-7890",
+        address=Address(
+            street="123 Main Street", city="Anytown", state="CA", zip_code="12345"
+        ),
+    )
+
+    assert contact is not None