A Merkle tree in blockchain is a data structure that is used to efficiently summarize and verify the integrity of the data stored in the blockchain. It is constructed by taking a list of data blocks, hashing each block, then combining pairs of hashes together and hashing them again until a single root hash, known as the Merkle root, is obtained. This Merkle root is then stored in the blockchain's block header, allowing for quick verification of the entire set of data without needing to access each individual block.
