In the history of finance, it has typically taken decades, if not centuries, for innovation to rise from first usage to the mainstream. However, that’s not been the case for cryptocurrencies and blockchain technology. Rather, it’s only taken a decade and a half.

15 years ago this month, Bitcoin, the original cryptocurrency, was first used in a real-world commercial transaction. This event is now known as “Bitcoin Pizza Day.” Every year, the crypto community celebrates this day, and how it represents how far this financial innovation has come from its humble beginnings.