diff --git a/packages/forest_admin_datasource_mongoid/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator.rb b/packages/forest_admin_datasource_mongoid/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator.rb
index 524ff4b9..47b6108b 100644
--- a/packages/forest_admin_datasource_mongoid/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator.rb
+++ b/packages/forest_admin_datasource_mongoid/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator.rb
@@ -26,6 +26,8 @@ def self.lookup_projection(current_path, schema_stack, projection, options)
             fields.merge!(add_fields(name, relation_projection, options))
           end
 
+          pipeline.push({ '$addFields' => fields }) unless fields.empty?
+
           pipeline
         end
 
@@ -36,7 +38,7 @@ def self.add_fields(name, projection, options)
           projection.filter { |field| field.include?('@@@') }
                     .map { |field_name| "#{name}.#{field_name.tr(":", ".")}" }
                     .each_with_object({}) do |curr, acc|
-                      acc[curr] = "$#{curr.tr("@@@", ".")}"
+                      acc[curr] = "$#{curr.gsub("@@@", ".")}"
                     end
         end
 
@@ -67,8 +69,10 @@ def self.lookup_relation(current_path, schema_stack, name, projection, options)
 
             return [
               # Push lookup to pipeline
-              { '$lookup' =>
-                { 'from' => from, 'localField' => local_field, 'foreignField' => foreign_field, 'as' => as } },
+              {
+                '$lookup' => { 'from' => from, 'localField' => local_field, 'foreignField' => foreign_field,
+                               'as' => as }
+              },
               { '$unwind' => { 'path' => "$#{as}", 'preserveNullAndEmptyArrays' => true } },
 
               # Recurse to get relations of relations
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/address.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/address.rb
index f8976409..4ce21a83 100644
--- a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/address.rb
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/address.rb
@@ -4,5 +4,6 @@ class Address
   field :city, type: String
   field :zip_code, type: String
 
+  embeds_one :meta, class_name: 'Meta'
   embedded_in :user
 end
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/author.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/author.rb
index ce60b3be..53b468fd 100644
--- a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/author.rb
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/author.rb
@@ -5,4 +5,5 @@ class Author
   field :last_name, type: String
 
   belongs_to :post
+  belongs_to :user
 end
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/co_author.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/co_author.rb
new file mode 100644
index 00000000..5f1b1118
--- /dev/null
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/co_author.rb
@@ -0,0 +1,8 @@
+class CoAuthor
+  include Mongoid::Document
+  include Mongoid::Timestamps
+  field :first_name, type: String
+  field :last_name, type: String
+
+  belongs_to :user
+end
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/meta.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/meta.rb
new file mode 100644
index 00000000..d27863e8
--- /dev/null
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/meta.rb
@@ -0,0 +1,6 @@
+class Meta
+  include Mongoid::Document
+  field :length, type: String
+
+  embedded_in :address
+end
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/post.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/post.rb
index 5e2ec981..161c16a9 100644
--- a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/post.rb
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/post.rb
@@ -8,4 +8,7 @@ class Post
   has_many :comments, dependent: :destroy
   has_one :author
   has_and_belongs_to_many :tags
+  belongs_to :user
+
+  embeds_one :co_author
 end
diff --git a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/user.rb b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/user.rb
index 0e206352..7ed17d57 100644
--- a/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/user.rb
+++ b/packages/forest_admin_datasource_mongoid/spec/dummy/app/models/user.rb
@@ -5,4 +5,5 @@ class User
   field :name, type: String
   belongs_to :item, polymorphic: true
   embeds_many :addresses
+  embeds_one :address
 end
diff --git a/packages/forest_admin_datasource_mongoid/spec/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator_spec.rb b/packages/forest_admin_datasource_mongoid/spec/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator_spec.rb
index ca98d553..da324b27 100644
--- a/packages/forest_admin_datasource_mongoid/spec/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator_spec.rb
+++ b/packages/forest_admin_datasource_mongoid/spec/lib/forest_admin_datasource_mongoid/utils/pipeline/lookup_generator_spec.rb
@@ -5,9 +5,9 @@ module Utils
     module Pipeline
       include ForestAdminDatasourceToolkit::Components::Query
       describe LookupGenerator do
-        let(:stack) { [{ prefix: nil, as_fields: [], as_models: [] }] }
-
         describe 'with the root collection' do
+          let(:stack) { [{ prefix: nil, as_fields: [], as_models: [] }] }
+
           it 'crashes when non-existent relations are asked for' do
             projection = Projection.new(['myAuthor:firstname'])
             expect do
@@ -29,28 +29,313 @@ module Pipeline
             expect(pipeline).to eq([])
           end
 
-          # TODO: when relations are totally implemented
-          # it 'should load the post (relation)' do
-          #   projection = Projection.new(['post__many_to_one:title'])
-          #   pipeline = LookupGenerator.lookup(Comment, stack, projection, {})
-          #
-          #   expect(pipeline).to eq([
-          #                            {
-          #                              '$lookup' => {
-          #                                'from' => 'posts',
-          #                                'localField' => 'post_id',
-          #                                'foreignField' => '_id',
-          #                                'as' => 'post__manyToOne'
-          #                              }
-          #                            },
-          #                            {
-          #                              '$unwind' => {
-          #                                'path' => '$post__manyToOne',
-          #                                'preserveNullAndEmptyArrays' => true
-          #                              }
-          #                            }
-          #                          ])
-          # end
+          it 'loads the post (relation)' do
+            projection = Projection.new(['post_id__many_to_one:title'])
+            pipeline = described_class.lookup(Comment, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'from' => 'Post',
+                    'localField' => 'post_id',
+                    'foreignField' => '_id',
+                    'as' => 'post_id__many_to_one'
+                  }
+                },
+                {
+                  '$unwind' => {
+                    'path' => '$post_id__many_to_one',
+                    'preserveNullAndEmptyArrays' => true
+                  }
+                }
+              ]
+            )
+          end
+
+          it 'loads the user (relation) with nested fields' do
+            projection = Projection.new(['user_id__many_to_one:address@@@city'])
+            pipeline = described_class.lookup(Post, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$addFields' => {
+                    'user_id__many_to_one.address@@@city' => '$user_id__many_to_one.address.city'
+                  }
+                }
+              ]
+            )
+          end
+
+          describe 'include' do
+            it 'returns the nested field if the parent is included' do
+              projection = Projection.new(['user_id__many_to_one:address@@@city'])
+              pipeline = described_class.lookup(Post, stack, projection, { include: ['user_id__many_to_one'] })
+
+              expect(pipeline).to eq(
+                [
+                  {
+                    '$lookup' => {
+                      'as' => 'user_id__many_to_one',
+                      'foreignField' => '_id',
+                      'from' => 'User',
+                      'localField' => 'user_id'
+                    }
+                  },
+                  { '$unwind' => { 'path' => '$user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                  {
+                    '$addFields' => {
+                      'user_id__many_to_one.address@@@city' => '$user_id__many_to_one.address.city'
+                    }
+                  }
+                ]
+              )
+            end
+
+            it 'does not add the nested field if the parent is not included' do
+              projection = Projection.new(['user_id__many_to_one:address@@@city'])
+              pipeline = described_class.lookup(Post, stack, projection, { include: [] })
+
+              expect(pipeline).to eq([])
+            end
+          end
+
+          describe 'exclude' do
+            it 'does not add the nested field if the parent is excluded' do
+              projection = Projection.new(['user_id__many_to_one:address@@@city'])
+              pipeline = described_class.lookup(Post, stack, projection, { exclude: ['user_id__many_to_one'] })
+
+              expect(pipeline).to eq([])
+            end
+
+            it 'does not add the nested field if the parent is not included' do
+              projection = Projection.new(['user_id__many_to_one:address@@@city'])
+              pipeline = described_class.lookup(Post, stack, projection, { exclude: [] })
+
+              expect(pipeline).to eq(
+                [
+                  {
+                    '$lookup' => {
+                      'as' => 'user_id__many_to_one',
+                      'foreignField' => '_id',
+                      'from' => 'User',
+                      'localField' => 'user_id'
+                    }
+                  },
+                  { '$unwind' => { 'path' => '$user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                  {
+                    '$addFields' => {
+                      'user_id__many_to_one.address@@@city' => '$user_id__many_to_one.address.city'
+                    }
+                  }
+                ]
+              )
+            end
+          end
+
+          it 'loads the user (relation) with double nested fields' do
+            projection = Projection.new(['user_id__many_to_one:address@@@meta@@@length'])
+            pipeline = described_class.lookup(Post, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$addFields' => {
+                    'user_id__many_to_one.address@@@meta@@@length' => '$user_id__many_to_one.address.meta.length'
+                  }
+                }
+              ]
+            )
+          end
+
+          it 'loads the post user city (double relation with nested field)' do
+            projection = Projection.new(['post_id__many_to_one:user_id__many_to_one:address@@@city'])
+            pipeline = described_class.lookup(Author, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'Post',
+                    'localField' => 'post_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one.user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'post_id__many_to_one.user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one.user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$addFields' => {
+                    'user_id__many_to_one.address@@@city' => '$user_id__many_to_one.address.city'
+                  }
+                },
+                {
+                  '$addFields' => {
+                    'post_id__many_to_one.user_id__many_to_one.address@@@city' => '$post_id__many_to_one.user_id__many_to_one.address.city'
+                  }
+                }
+              ]
+            )
+          end
+
+          it 'loads the post user address meta length (double relation with double nested field)' do
+            projection = Projection.new(['post_id__many_to_one:user_id__many_to_one:address@@@meta@@@length'])
+            pipeline = described_class.lookup(Author, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'Post',
+                    'localField' => 'post_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one.user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'post_id__many_to_one.user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one.user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$addFields' => {
+                    'user_id__many_to_one.address@@@meta@@@length' => '$user_id__many_to_one.address.meta.length'
+                  }
+                },
+                {
+                  '$addFields' => {
+                    'post_id__many_to_one.user_id__many_to_one.address@@@meta@@@length' => '$post_id__many_to_one.user_id__many_to_one.address.meta.length'
+                  }
+                }
+              ]
+            )
+          end
+
+          it 'loads the post co_author user (relation within fake relation)' do
+            projection = Projection.new(['co_author:user_id__many_to_one:name'])
+            pipeline = described_class.lookup(Post, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'co_author.user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'co_author.user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$co_author.user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } }
+              ]
+            )
+          end
+
+          it 'loads the comment post user (nested relation)' do
+            projection = Projection.new(['post_id__many_to_one:user_id__many_to_one:name'])
+            pipeline = described_class.lookup(Comment, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'Post',
+                    'localField' => 'post_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one', 'preserveNullAndEmptyArrays' => true } },
+                {
+                  '$lookup' => {
+                    'as' => 'post_id__many_to_one.user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'post_id__many_to_one.user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$post_id__many_to_one.user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } }
+              ]
+            )
+          end
+        end
+
+        describe 'with a reparented collection' do
+          let(:stack) do
+            [
+              { prefix: nil, as_fields: [], as_models: ['co_author'] },
+              { prefix: 'co_author', as_fields: [], as_models: [] }
+            ]
+          end
+
+          it 'loads the post co_author user (relation)' do
+            projection = Projection.new(['user_id__many_to_one:name'])
+            pipeline = described_class.lookup(Post, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } }
+              ]
+            )
+          end
+
+          it 'loads the user (relation within fake relation)' do
+            projection = Projection.new(['parent:user_id__many_to_one:name'])
+            pipeline = described_class.lookup(Post, stack, projection, {})
+
+            expect(pipeline).to eq(
+              [
+                {
+                  '$lookup' => {
+                    'as' => 'parent.user_id__many_to_one',
+                    'foreignField' => '_id',
+                    'from' => 'User',
+                    'localField' => 'parent.user_id'
+                  }
+                },
+                { '$unwind' => { 'path' => '$parent.user_id__many_to_one', 'preserveNullAndEmptyArrays' => true } }
+              ]
+            )
+          end
         end
       end
     end