diff --git a/opal/clearwater/black_box_node.rb b/opal/clearwater/black_box_node.rb
index 27fd147..22a60d4 100644
--- a/opal/clearwater/black_box_node.rb
+++ b/opal/clearwater/black_box_node.rb
@@ -20,9 +20,15 @@ def render
       Renderable.new(self)
     end
 
+    def key
+    end
+
     class Renderable
       def initialize delegate
         @delegate = delegate
+        if delegate.key
+          @key = delegate.key
+        end
       end
 
       def wrap node
@@ -52,7 +58,14 @@ def create_element
         //   node: a Bowser-wrapped version of the DOM node
         Opal.defn(self, 'update', function(previous, node) {
           var self = this;
-          #{@delegate.update(`previous.delegate`, wrap(`node`))};
+          if(self.delegate.$$class === previous.delegate.$$class) {
+            #{@delegate.update(`previous.delegate`, wrap(`node`))};
+          } else {
+            previous.destroy(#{wrap(`node`)});
+            var new_node = #{create_element};
+            #{@delegate.mount(`new_node`)};
+            return new_node.native;
+          }
         });
 
         // virtual-dom destroy hook
diff --git a/opal/clearwater/cached_render.rb b/opal/clearwater/cached_render.rb
index be13d21..238fcd7 100644
--- a/opal/clearwater/cached_render.rb
+++ b/opal/clearwater/cached_render.rb
@@ -13,7 +13,6 @@ def should_render? _
     end
 
     def key
-      `undefined`
     end
   end
 end
diff --git a/opal/clearwater/cached_render/wrapper.rb b/opal/clearwater/cached_render/wrapper.rb
index 8c291d0..48aba05 100644
--- a/opal/clearwater/cached_render/wrapper.rb
+++ b/opal/clearwater/cached_render/wrapper.rb
@@ -5,7 +5,7 @@ class Wrapper
 
       def initialize content
         @content = content
-        @key = content.key
+        @key = content.key if content.key
       end
 
       # Hook into vdom diff/patch
diff --git a/opal/clearwater/memoized_component.rb b/opal/clearwater/memoized_component.rb
new file mode 100644
index 0000000..6dcbcd9
--- /dev/null
+++ b/opal/clearwater/memoized_component.rb
@@ -0,0 +1,75 @@
+require 'clearwater/component'
+require 'clearwater/black_box_node'
+
+module Clearwater
+  class MemoizedComponent
+    include Clearwater::Component
+
+    def self.memoize *args, &block
+      Placeholder.new(self, args, block)
+    end
+
+    def self.[] key
+      memoize[key]
+    end
+
+    def update
+    end
+
+    def destroy
+    end
+
+    class Placeholder
+      include Clearwater::BlackBoxNode
+
+      attr_reader :klass, :key, :vdom
+
+      def initialize klass, args, block
+        @klass = klass
+        @args = args
+        @block = block
+      end
+
+      def memoize *args, &block
+        initialize @klass, args, block
+        self
+      end
+
+      def [] key
+        @key = key.to_s
+        self
+      end
+
+      def component
+        @component ||= @klass.new(*@args, &@block)
+      end
+
+      def node
+        @node ||= Clearwater::Component.sanitize_content(component)
+      end
+
+      def mount element
+        @vdom = VirtualDOM::Document.new(element)
+
+        # TODO: add a public interface to generate a pre-initialized VDOM::Doc
+        `#@vdom.tree = #{element.to_n}`
+        `#@vdom.node = #{node}`
+        `#@vdom.rendered = true`
+      end
+
+      def update previous
+        @vdom = previous.vdom
+        @component = previous.component
+
+        if component.should_update?(*@args, &@block)
+          component.update(*@args, &@block)
+          @vdom.render component.render
+        end
+      end
+
+      def unmount
+        component.destroy
+      end
+    end
+  end
+end
diff --git a/opal/clearwater/virtual_dom.rb b/opal/clearwater/virtual_dom.rb
index 5607abf..4e23f21 100644
--- a/opal/clearwater/virtual_dom.rb
+++ b/opal/clearwater/virtual_dom.rb
@@ -46,7 +46,7 @@ def self.sanitize_content content
     end
 
     class Document
-      def initialize(root=Bowser.document.create_element('div'))
+      def initialize(root=Bowser.document.create_element(:div))
         @root = root
       end
 
diff --git a/spec-opal/clearwater/black_box_node_spec.rb b/spec-opal/clearwater/black_box_node_spec.rb
index e2d2680..d81c6d2 100644
--- a/spec-opal/clearwater/black_box_node_spec.rb
+++ b/spec-opal/clearwater/black_box_node_spec.rb
@@ -29,7 +29,7 @@ def mounted?
         end
       end.new
     }
-    let(:renderable) { BlackBoxNode::Renderable.new(object) }
+    let(:renderable) { object.render }
 
     it 'has the special type of "Widget"' do
       r = renderable
@@ -55,8 +55,7 @@ def mounted?
     end
 
     it 'calls update when updated in the DOM' do
-      r = renderable
-      `r.update({})`
+      `#{renderable}.update(#{renderable.dup})`
 
       expect(object.last_update).not_to be_nil
     end