diff --git a/mongomap/__init__.py b/mongomap/__init__.py
index 214f0fa4..1b7da2b3 100644
--- a/mongomap/__init__.py
+++ b/mongomap/__init__.py
@@ -1,8 +1,9 @@
-from document import Document
+import document
+from document import *
 import fields
 from fields import *
 
-__all__ = fields.__all__  + ['Document']
+__all__ = document.__all__ + fields.__all__
 
 __author__ = 'Harry Marr'
 __version__ = '0.1'
diff --git a/mongomap/base.py b/mongomap/base.py
index f6c97faa..f4be1fb7 100644
--- a/mongomap/base.py
+++ b/mongomap/base.py
@@ -161,3 +161,8 @@ class BaseDocument(object):
         if name not in self._fields:
             raise KeyError(name)
         return setattr(self, name, value)
+
+    def _to_mongo(self):
+        """Return data dictionary ready for use with MongoDB.
+        """
+        return dict((k, v) for k, v in self._data.items() if v is not None)
diff --git a/mongomap/document.py b/mongomap/document.py
index 3fe2bb31..b1b3ffe3 100644
--- a/mongomap/document.py
+++ b/mongomap/document.py
@@ -2,6 +2,10 @@ from base import DocumentMetaclass, TopLevelDocumentMetaclass, BaseDocument
 
 #import pymongo
 
+
+__all__ = ['Document', 'EmbeddedDocument']
+
+
 class EmbeddedDocument(BaseDocument):
     
     __metaclass__ = DocumentMetaclass
diff --git a/mongomap/fields.py b/mongomap/fields.py
index b8fe9693..6235cb6d 100644
--- a/mongomap/fields.py
+++ b/mongomap/fields.py
@@ -4,7 +4,8 @@ from document import EmbeddedDocument
 import re
 
 
-__all__ = ['StringField', 'IntField', 'ValidationError']
+__all__ = ['StringField', 'IntField', 'EmbeddedDocumentField', 
+           'ValidationError']
 
 
 class StringField(BaseField):
@@ -52,7 +53,15 @@ class EmbeddedDocumentField(BaseField):
 
     def __init__(self, document, **kwargs):
         if not issubclass(document, EmbeddedDocument):
-            raise ValidationError('Invalid embedded document provided to an '
-                                  'EmbeddedDocumentField')
+            raise ValidationError('Invalid embedded document class provided '
+                                  'to an EmbeddedDocumentField')
         self.document = document
         super(EmbeddedDocumentField, self).__init__(**kwargs)
+    
+    def _to_python(self, value):
+        return value
+
+    def _validate(self, value):
+        if not isinstance(value, self.document):
+            raise ValidationError('Invalid embedded document instance '
+                                  'provided to an EmbeddedDocumentField')
diff --git a/tests/fields.py b/tests/fields.py
index 973ee8db..58342453 100644
--- a/tests/fields.py
+++ b/tests/fields.py
@@ -65,6 +65,28 @@ class FieldTest(unittest.TestCase):
         self.assertRaises(ValidationError, person.__setattr__, 'age', 120)
         self.assertRaises(ValidationError, person.__setattr__, 'age', 'ten')
 
+    def test_embedded_document_validation(self):
+        """Ensure that invalid embedded documents cannot be assigned to
+        embedded document fields.
+        """
+        class Comment(EmbeddedDocument):
+            content = StringField()
+
+        class PersonPreferences(EmbeddedDocument):
+            food = StringField()
+            number = IntField()
+
+        class Person(Document):
+            name = StringField()
+            preferences = EmbeddedDocumentField(PersonPreferences)
+
+        person = Person(name='Test User')
+        self.assertRaises(ValidationError, person.__setattr__, 'preferences', 
+                          'My preferences')
+        self.assertRaises(ValidationError, person.__setattr__, 'preferences', 
+                          Comment(content='Nice blog post...'))
+        person.preferences = PersonPreferences(food='Cheese', number=47)
+
 
 if __name__ == '__main__':
     unittest.main()