# Transactions

Each data record written to the blockchain (whether it is an [asset creation](https://teos-docs.coreledger.net/resources/using-the-teos-api/concepts/asset), one of the [spark operations](https://teos-docs.coreledger.net/resources/using-the-teos-api/concepts/spark#spark-operations), [supply creation and update](https://teos-docs.coreledger.net/resources/using-the-teos-api/concepts/supply) or any other transaction type) is a blockchain transaction. Writing data to the blockchain requires a valid signature to call functions of a smart contract. The data is entered into the blockchain in intervals known as blocks. Each block is time stamped and its order and transactions are verified.

📘 [Learn more ](https://teos-docs.coreledger.net/resources/using-the-teos-api/concepts/transaction)about transactions.