State: Great arbitrary storage space, arbitrary code (isolated memory space), and account balance. An Ethereum block consists of merkle-like trees hashes - a tree hash of state (code, account balance, nonce, and storage) - a tree hash for updates which is a collection of transactions. Payment: from:sender, to:recipient, sender, value:$, (value) optional: data, gas_price:transaction fee Contract call: to: contract address, from:sender, value:$, data: f(), args, start_gas: how much computation are you willing to pay for Contract create: to: null, from:sender, data: code, value: initial balance, start_gas: pay for contract creation