diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index 459373eeae..48aa830e77 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -23,6 +23,10 @@ func (db *MemDatabase) Put(key []byte, value []byte) {
 	db.db[string(key)] = value
 }
 
+func (db *MemDatabase) Set(key []byte, value []byte) {
+	db.Put(key, value)
+}
+
 func (db *MemDatabase) Get(key []byte) ([]byte, error) {
 	return db.db[string(key)], nil
 }
diff --git a/ptrie/fullnode.go b/ptrie/fullnode.go
index eaa4611b66..7a7f7d22d4 100644
--- a/ptrie/fullnode.go
+++ b/ptrie/fullnode.go
@@ -18,7 +18,14 @@ func (self *FullNode) Branches() []Node {
 	return self.nodes[:16]
 }
 
-func (self *FullNode) Copy() Node { return self }
+func (self *FullNode) Copy() Node {
+	nnode := NewFullNode(self.trie)
+	for i, node := range self.nodes {
+		nnode.nodes[i] = node
+	}
+
+	return nnode
+}
 
 // Returns the length of non-nil nodes
 func (self *FullNode) Len() (amount int) {
diff --git a/ptrie/shortnode.go b/ptrie/shortnode.go
index 49319c555d..73ff2914bf 100644
--- a/ptrie/shortnode.go
+++ b/ptrie/shortnode.go
@@ -17,7 +17,7 @@ func (self *ShortNode) Value() Node {
 	return self.value
 }
 func (self *ShortNode) Dirty() bool { return true }
-func (self *ShortNode) Copy() Node  { return self }
+func (self *ShortNode) Copy() Node  { return NewShortNode(self.trie, self.key, self.value) }
 
 func (self *ShortNode) RlpData() interface{} {
 	return []interface{}{self.key, self.value.Hash()}
diff --git a/ptrie/trie.go b/ptrie/trie.go
index bb2b3845ad..687126aef8 100644
--- a/ptrie/trie.go
+++ b/ptrie/trie.go
@@ -2,6 +2,7 @@ package ptrie
 
 import (
 	"bytes"
+	"container/list"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/crypto"
@@ -14,33 +15,61 @@ type Backend interface {
 	Set([]byte, []byte)
 }
 
-type Cache map[string][]byte
-
-func (self Cache) Get(key []byte) []byte {
-	return self[string(key)]
+type Cache struct {
+	store   map[string][]byte
+	backend Backend
 }
-func (self Cache) Set(key []byte, data []byte) {
-	self[string(key)] = data
+
+func NewCache(backend Backend) *Cache {
+	return &Cache{make(map[string][]byte), backend}
+}
+
+func (self *Cache) Get(key []byte) []byte {
+	data := self.store[string(key)]
+	if data == nil {
+		data = self.backend.Get(key)
+	}
+
+	return data
+}
+
+func (self *Cache) Set(key []byte, data []byte) {
+	self.store[string(key)] = data
+}
+
+func (self *Cache) Flush() {
+	for k, v := range self.store {
+		self.backend.Set([]byte(k), v)
+	}
+
+	// This will eventually grow too large. We'd could
+	// do a make limit on storage and push out not-so-popular nodes.
+	//self.Reset()
+}
+
+func (self *Cache) Reset() {
+	self.store = make(map[string][]byte)
 }
 
 type Trie struct {
 	mu       sync.Mutex
 	root     Node
 	roothash []byte
-	backend  Backend
-}
+	cache    *Cache
 
-func NewEmpty() *Trie {
-	return &Trie{sync.Mutex{}, nil, nil, make(Cache)}
+	revisions *list.List
 }
 
 func New(root []byte, backend Backend) *Trie {
 	trie := &Trie{}
+	trie.revisions = list.New()
 	trie.roothash = root
-	trie.backend = backend
+	trie.cache = NewCache(backend)
 
-	value := ethutil.NewValueFromBytes(trie.backend.Get(root))
-	trie.root = trie.mknode(value)
+	if root != nil {
+		value := ethutil.NewValueFromBytes(trie.cache.Get(root))
+		trie.root = trie.mknode(value)
+	}
 
 	return trie
 }
@@ -64,10 +93,28 @@ func (self *Trie) Hash() []byte {
 		hash = crypto.Sha3(ethutil.Encode(self.root))
 	}
 
-	self.roothash = hash
+	if !bytes.Equal(hash, self.roothash) {
+		self.revisions.PushBack(self.roothash)
+		self.roothash = hash
+	}
 
 	return hash
 }
+func (self *Trie) Commit() {
+	// Hash first
+	self.Hash()
+
+	self.cache.Flush()
+}
+
+func (self *Trie) Reset() {
+	self.cache.Reset()
+
+	revision := self.revisions.Remove(self.revisions.Back()).([]byte)
+	self.roothash = revision
+	value := ethutil.NewValueFromBytes(self.cache.Get(self.roothash))
+	self.root = self.mknode(value)
+}
 
 func (self *Trie) UpdateString(key, value string) Node { return self.Update([]byte(key), []byte(value)) }
 func (self *Trie) Update(key, value []byte) Node {
@@ -272,7 +319,7 @@ func (self *Trie) mknode(value *ethutil.Value) Node {
 func (self *Trie) trans(node Node) Node {
 	switch node := node.(type) {
 	case *HashNode:
-		value := ethutil.NewValueFromBytes(self.backend.Get(node.key))
+		value := ethutil.NewValueFromBytes(self.cache.Get(node.key))
 		return self.mknode(value)
 	default:
 		return node
@@ -283,7 +330,7 @@ func (self *Trie) store(node Node) interface{} {
 	data := ethutil.Encode(node)
 	if len(data) >= 32 {
 		key := crypto.Sha3(data)
-		self.backend.Set(key, data)
+		self.cache.Set(key, data)
 
 		return key
 	}
diff --git a/ptrie/trie_test.go b/ptrie/trie_test.go
index 6af6e1b406..478f59c602 100644
--- a/ptrie/trie_test.go
+++ b/ptrie/trie_test.go
@@ -8,6 +8,16 @@ import (
 	"github.com/ethereum/go-ethereum/ethutil"
 )
 
+type Db map[string][]byte
+
+func (self Db) Get(k []byte) []byte { return self[string(k)] }
+func (self Db) Set(k, v []byte)     { self[string(k)] = v }
+
+// Used for testing
+func NewEmpty() *Trie {
+	return New(nil, make(Db))
+}
+
 func TestInsert(t *testing.T) {
 	trie := NewEmpty()
 
@@ -91,7 +101,7 @@ func TestReplication(t *testing.T) {
 	}
 	trie.Hash()
 
-	trie2 := New(trie.roothash, trie.backend)
+	trie2 := New(trie.roothash, trie.cache)
 	if string(trie2.GetString("horse")) != "stallion" {
 		t.Error("expected to have harse => stallion")
 	}
@@ -104,6 +114,53 @@ func TestReplication(t *testing.T) {
 
 }
 
+func TestReset(t *testing.T) {
+	trie := NewEmpty()
+	vals := []struct{ k, v string }{
+		{"do", "verb"},
+		{"ether", "wookiedoo"},
+		{"horse", "stallion"},
+	}
+	for _, val := range vals {
+		trie.UpdateString(val.k, val.v)
+	}
+	trie.Commit()
+
+	before := ethutil.CopyBytes(trie.roothash)
+	trie.UpdateString("should", "revert")
+	trie.Hash()
+	// Should have no effect
+	trie.Hash()
+	trie.Hash()
+	// ###
+
+	trie.Reset()
+	after := ethutil.CopyBytes(trie.roothash)
+
+	if !bytes.Equal(before, after) {
+		t.Errorf("expected roots to be equal. %x - %x", before, after)
+	}
+}
+
+// Not actual test
+func TestOutput(t *testing.T) {
+	t.Skip()
+
+	base := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+	trie := NewEmpty()
+	for i := 0; i < 50; i++ {
+		trie.UpdateString(fmt.Sprintf("%s%d", base, i), "valueeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee")
+	}
+	trie.Hash()
+	fmt.Println("############################## FULL ################################")
+	fmt.Println(trie.root)
+
+	trie2 := New(trie.roothash, trie.cache)
+	trie2.GetString(base + "20")
+	fmt.Println("############################## SMALL ################################")
+	fmt.Println(trie2.root)
+}
+
 func BenchmarkGets(b *testing.B) {
 	trie := NewEmpty()
 	vals := []struct{ k, v string }{
@@ -136,22 +193,3 @@ func BenchmarkUpdate(b *testing.B) {
 	}
 	trie.Hash()
 }
-
-// Not actual test
-func TestOutput(t *testing.T) {
-	t.Skip()
-
-	base := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
-	trie := NewEmpty()
-	for i := 0; i < 50; i++ {
-		trie.UpdateString(fmt.Sprintf("%s%d", base, i), "valueeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee")
-	}
-	trie.Hash()
-	fmt.Println("############################## FULL ################################")
-	fmt.Println(trie.root)
-
-	trie2 := New(trie.roothash, trie.backend)
-	trie2.GetString(base + "20")
-	fmt.Println("############################## SMALL ################################")
-	fmt.Println(trie2.root)
-}
diff --git a/ptrie/valuenode.go b/ptrie/valuenode.go
index c226621a70..c593eb6c60 100644
--- a/ptrie/valuenode.go
+++ b/ptrie/valuenode.go
@@ -8,6 +8,6 @@ type ValueNode struct {
 func (self *ValueNode) Value() Node          { return self } // Best not to call :-)
 func (self *ValueNode) Val() []byte          { return self.data }
 func (self *ValueNode) Dirty() bool          { return true }
-func (self *ValueNode) Copy() Node           { return self }
+func (self *ValueNode) Copy() Node           { return &ValueNode{self.trie, self.data} }
 func (self *ValueNode) RlpData() interface{} { return self.data }
 func (self *ValueNode) Hash() interface{}    { return self.data }