diff --git a/eth/main.cpp b/eth/main.cpp
index 95026956d..0af33fb81 100644
--- a/eth/main.cpp
+++ b/eth/main.cpp
@@ -31,9 +31,9 @@ int main()
 	// Our address.
 	Address us;				// TODO: should be loaded from config file/set at command-line.
 
-	BlockChain bc;			// TODO: Implement - should maintain block database.
-	TransactionQueue tq;	// TODO: Implement.
-	State s(us);			// TODO: Switch to disk-backed state (leveldb)
+	BlockChain bc;			// Maintains block database.
+	TransactionQueue tq;	// Maintains list of incoming transactions not yet on the block chain.
+	State s(us);			// TODO: Switch to disk-backed state (leveldb? could do with a diffing DB)
 //	s.restore();			// TODO: Implement - key optimisation.
 
 	// Synchronise the state according to the block chain - i.e. replay all transactions, in order. Will take a while if the state isn't restored.
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index 34ba1d0bb..3593d3f26 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -38,7 +38,8 @@ BlockChain::BlockChain()
 	m_lastBlockHash = m_genesisHash = BlockInfo::genesis().hash;
 	m_genesisBlock = BlockInfo::createGenesisBlock();
 
-	// TODO: Insert details of genesis block.
+	// Insert details of genesis block.
+	m_details[m_genesisHash] = { 0, (u256)1 << 36, h256(), {} };
 }
 
 BlockChain::~BlockChain()
@@ -57,8 +58,7 @@ h256s BlockChain::blockChain(h256Set const& _earlyExit) const
 	ret.push_back(i);
 	return ret;
 }
-// _bc.details(m_previousBlock.parentHash).children
-// _bc->coinbaseAddress(i)
+
 void BlockChain::import(bytes const& _block)
 {
 	try
diff --git a/libethereum/BlockChain.h b/libethereum/BlockChain.h
index 59b13294f..f00c68fd2 100644
--- a/libethereum/BlockChain.h
+++ b/libethereum/BlockChain.h
@@ -36,7 +36,7 @@ struct BlockDetails
 	h256s children;
 };
 
-static const BlockDetails NullBlockDetails({0, 0, h256()});
+static const BlockDetails NullBlockDetails({ 0, 0, h256(), {} });
 static const h256s NullH256s;
 
 /**
diff --git a/libethereum/BlockInfo.cpp b/libethereum/BlockInfo.cpp
index 9c169cc77..7b451cbe7 100644
--- a/libethereum/BlockInfo.cpp
+++ b/libethereum/BlockInfo.cpp
@@ -50,7 +50,14 @@ bytes BlockInfo::createGenesisBlock()
 
 h256 BlockInfo::headerHashWithoutNonce() const
 {
-	return sha3((RLPStream(7) << toBigEndianString(parentHash) << toBigEndianString(sha3Uncles) << coinbaseAddress << toBigEndianString(stateRoot) << toBigEndianString(sha3Transactions) << difficulty << timestamp).out());
+	return sha3((RLPStream(7) << parentHash << sha3Uncles << coinbaseAddress << stateRoot << sha3Transactions << difficulty << timestamp).out());
+}
+
+void BlockInfo::fillStream(RLPStream& _s, bool _nonce) const
+{
+	_s.appendList(_nonce ? 8 : 7) << parentHash << sha3Uncles << coinbaseAddress << stateRoot << sha3Transactions << difficulty << timestamp;
+	if (_nonce)
+		_s << nonce;
 }
 
 void BlockInfo::populateGenesis()
diff --git a/libethereum/BlockInfo.h b/libethereum/BlockInfo.h
index 2ec47e5e7..1fbd8e2fe 100644
--- a/libethereum/BlockInfo.h
+++ b/libethereum/BlockInfo.h
@@ -46,6 +46,7 @@ public:
 	explicit operator bool() const { return timestamp != Invalid256; }
 
 	bool operator==(BlockInfo const& _cmp) const { return hash == _cmp.hash && parentHash == _cmp.parentHash && nonce == _cmp.nonce; }
+	bool operator!=(BlockInfo const& _cmp) const { return !operator==(_cmp); }
 
 	static BlockInfo const& genesis() { if (!s_genesis) (s_genesis = new BlockInfo)->populateGenesis(); return *s_genesis; }
 	void populate(bytesConstRef _block);
@@ -56,6 +57,7 @@ public:
 
 	/// No-nonce sha3 of the header only.
 	h256 headerHashWithoutNonce() const;
+	void fillStream(RLPStream& _s, bool _nonce) const;
 
 	static bytes createGenesisBlock();
 
diff --git a/libethereum/RLP.h b/libethereum/RLP.h
index 268e8c1b1..39da78a5a 100644
--- a/libethereum/RLP.h
+++ b/libethereum/RLP.h
@@ -315,6 +315,8 @@ public:
 	/// Read the byte stream.
 	bytes const& out() const { return m_out; }
 
+	void swapOut(bytes& _dest) { swap(m_out, _dest); }
+
 private:
 	/// Push the node-type byte (using @a _base) along with the item count @a _count.
 	/// @arg _count is number of characters for strings, data-bytes for ints, or items for lists.
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index ff0e4cbe9..cbdde75a5 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -45,6 +45,7 @@ State::State(Address _coinbaseAddress): m_ourAddress(_coinbaseAddress)
 {
 	secp256k1_start();
 	m_previousBlock = BlockInfo::genesis();
+	m_currentBlock.coinbaseAddress = m_ourAddress;
 }
 
 void State::sync(BlockChain const& _bc)
@@ -77,6 +78,7 @@ void State::sync(BlockChain const& _bc, h256 _block)
 		m_current.clear();
 		m_transactions.clear();
 		m_currentBlock = BlockInfo();
+		m_currentBlock.coinbaseAddress = m_ourAddress;
 		++m_currentNumber;
 	}
 	else if (bi == m_previousBlock)
@@ -109,6 +111,7 @@ void State::sync(BlockChain const& _bc, h256 _block)
 		m_current.clear();
 		m_currentBlock = BlockInfo();
 		m_currentNumber = _bc.details(_bc.currentHash()).number + 1;
+		m_currentBlock.coinbaseAddress = m_ourAddress;
 	}
 }
 
@@ -198,6 +201,40 @@ u256 State::playback(bytesConstRef _block, BlockInfo const& _grandParent)
 	return tdIncrease;
 }
 
+// @returns the block that represents the difference between m_previousBlock and m_currentBlock.
+// (i.e. all the transactions we executed).
+bytes State::compileBlock(BlockChain const& _bc)
+{
+	RLPStream uncles;
+	if (m_previousBlock != BlockInfo::genesis())
+	{
+		// Find uncles if we're not a direct child of the genesis.
+		auto us = _bc.details(m_previousBlock.parentHash).children;
+		uncles.appendList(us.size());
+		for (auto const& u: us)
+			BlockInfo(_bc.block(u)).fillStream(uncles, true);
+	}
+	else
+		uncles.appendList(0);
+
+	RLPStream txs(m_transactions.size());
+	for (auto const& i: m_transactions)
+		i.second.fillStream(txs);
+
+	txs.swapOut(m_currentTxs);
+	uncles.swapOut(m_currentUncles);
+
+	m_currentBlock.sha3Transactions = sha3(m_currentTxs);
+	m_currentBlock.sha3Uncles = sha3(m_currentUncles);
+
+	RLPStream ret;
+	ret.appendList(3);
+	m_currentBlock.fillStream(ret, true);
+	ret.appendRaw(m_currentTxs);
+	ret.appendRaw(m_currentUncles);
+	return ret.out();
+}
+
 h256 State::rootHash() const
 {
 	// TODO!
diff --git a/libethereum/State.h b/libethereum/State.h
index e84fa23d7..98d3ae539 100644
--- a/libethereum/State.h
+++ b/libethereum/State.h
@@ -114,6 +114,8 @@ public:
 	/// This might throw.
 	u256 playback(bytesConstRef _block, BlockInfo const& _bi, BlockInfo const& _parent, BlockInfo const& _grandParent);
 
+	bytes compileBlock(BlockChain const& _bc);
+
 private:
 	/// Fee-adder on destruction RAII class.
 	struct MinerFeeAdder
@@ -147,6 +149,9 @@ private:
 	bytes m_currentBytes;						///< The current block.
 	uint m_currentNumber;
 
+	bytes m_currentTxs;
+	bytes m_currentUncles;
+
 	Address m_ourAddress;					///< Our address (i.e. the address to which fees go).
 
 	/// The fee structure. Values yet to be agreed on...
diff --git a/libethereum/Trie.cpp b/libethereum/Trie.cpp
index d64ca3d30..12ed53831 100644
--- a/libethereum/Trie.cpp
+++ b/libethereum/Trie.cpp
@@ -200,6 +200,19 @@ h256 hash256(StringMap const& _s)
 	return sha3(s.out());
 }
 
+bytes rlp256(StringMap const& _s)
+{
+	// build patricia tree.
+	if (_s.empty())
+		return RLPNull;
+	HexMap hexMap;
+	for (auto i = _s.rbegin(); i != _s.rend(); ++i)
+		hexMap[toHex(i->first)] = i->second;
+	RLPStream s;
+	hash256aux(hexMap, hexMap.cbegin(), hexMap.cend(), 0, s);
+	return s.out();
+}
+
 h256 hash256(u256Map const& _s)
 {
 	// build patricia tree.
diff --git a/libethereum/Trie.h b/libethereum/Trie.h
index 1a6bdc73b..c80b30790 100644
--- a/libethereum/Trie.h
+++ b/libethereum/Trie.h
@@ -27,6 +27,7 @@
 namespace eth
 {
 
+bytes rlp256(StringMap const& _s);
 h256 hash256(StringMap const& _s);
 h256 hash256(u256Map const& _s);
 std::string hexPrefixEncode(bytes const& _hexVector, bool _terminated = false, int _begin = 0, int _end = -1);
diff --git a/test/main.cpp b/test/main.cpp
index 3587a1ee6..35f3fc20d 100644
--- a/test/main.cpp
+++ b/test/main.cpp
@@ -36,6 +36,7 @@ using namespace eth;
 
 int main()
 {
+/*
 	// Test dagger
 	{
 		Dagger d((h256)0);
@@ -53,6 +54,7 @@ int main()
 		cout << hex << d.eval(1);
 		cout << " " << dec << duration_cast<milliseconds>(steady_clock::now() - s).count() << " ms" << endl;
 	}
+	*/
 /*
 	// Test transaction.
 	bytes tx = fromUserHex("88005401010101010101010101010101010101010101011f0de0b6b3a76400001ce8d4a5100080181c373130a009ba1f10285d4e659568bfcfec85067855c5a3c150100815dad4ef98fd37cf0593828c89db94bd6c64e210a32ef8956eaa81ea9307194996a3b879441f5d");
@@ -111,6 +113,9 @@ int main()
 		cout << "SENDER: " << hex << low160(eth::sha3(bytesConstRef(&pubkey).cropped(1))) << endl;
 	}
 */
+	cout << escaped(asString(rlp256({{"b", "B"}, {"a", "A"}})), false) << " == " << RLP(rlp256({{"b", "B"}, {"a", "A"}})) << endl;
+	cout << escaped(asString(rlp256({{"test", "test"}})), false) << " == " << RLP(rlp256({{"test", "test"}})) << endl;
+	cout << asHex(rlp256({{"test", "test"}, {"te", "test"}})) << endl;
 	{
 		Trie t;
 		t.insert("dog", "puppy");