Blockchain structure

Blockchains are structured as a series of linked blocks, each containing a number of transactions. Each block is chained to the previous block by including the hash of the previous block in its header. This means that any changes to a block in the chain would invalidate all subsequent blocks.

The blockchain structure is designed to make it very tamper-proof. If someone tried to change a block in the chain, they would have to recalculate all subsequent blocks as well. This would be a very computationally expensive task, and it is unlikely that anyone would be able to do it without being detected.