Blockchain high resolution photo set.
A blockchain is a growing list of records, known as blocks, that are cryptographically linked together. A cryptographic hash of the preceding block, a timestamp, and transaction data are all included in each block (generally represented as a Merkle tree, where data nodes are represented by leafs). The timestamp verifies that the transaction data was there at the time the block was released, allowing it to be hashed. Because each block contains information about the one before it, they form a chain, with each new block reinforcing the preceding ones. As a result, blockchains are resistant to data tampering since the data in any given block, once recorded, cannot be changed retrospectively without affecting all subsequent blocks.