The data that is added over time are structures called blocks. Blocks build one on top of another in chronological order and include a piece of information that links the data block to the previous block, creating a chain all the way back to the genesis block (the first block). Blockchain is the core underlying component of cryptocurrencies. The reason blockchain is considered one of the most disruptive technologies is its decentralized, ie. trustless, nature, that the truth of a state (facts, data, financial balances) is kept and maintained without relying on a centralized third party (centralized databases, financial institutions, authorities).