On Saturday, January 3, 2009, Bitcoin was born. With the creation of the very first Bitcoin block—known as the ‘Genesis Block’—the first set of 50 BTC was mined into existence.This genesis block is considered the start of the Bitcoin blockchain—and the beginning of the cryptocurrency revolution.Many would argue that the day it was minted represents Bitcoin’s birthday. Though others instead believe that Bitcoin’s birthday is actually three months earlier—when the Bitcoin whitepaper was first released.As the first block ever created, the genesis block is the start of the immutable database that is the Bitcoin blockchain, and represents the first example of a peer-to-peer digital currency secured by sound cryptographic principles. But unlike other blocks, it has several unique properties, adding a layer of hidden meaning that might not be apparent at first glance.What is a Genesis Block?A genesis block is simply the first block mined on a blockchain network.Blocks are typically added to blockchains either by miners (on proof-of-work networks such as Bitcoin) or validators (on proof-of-stake networks such as Ethereum). Each new block records transactions and references the previous block in the chain.However, because the genesis block initiates the blockchain and doesn’t have any previous blocks to refer back to, it is created by the blockchain’s developers. In the case of Bitcoin, that’s its pseudonymous creator, Satoshi Nakamoto.The genesis block establishes the rules under which the blockchain operates, such as mining difficulty and block rewards. Bitcoin’s genesis block set the reward for mining a block at 50 BTC, which halves approximately every four years until its supply cap of 21 million BTC is reached.