Block Header

The block header is an 80-byte long string. It is comprised of the 4-byte long Bitcoin version number, 32-byte previous block hash, 32-byte long merkle root, 4-byte long timestamp of the block, 4-byte long difficulty target for the block, and 4-byte long nonce used by miners. Miners will repetitively hash the block header in order to find the correct nouns that will permit them to mine the next block. All previous headers are referenced in every block of the chain.