Most fiat monies are divisible into 100 smaller units, such as the US Dollar and its cent or the Pound Sterling and its penny. In a similar way, each bitcoin is divisible into 100 million smaller units called ‘satoshi’, after the inventor of Bitcoin, Satoshi Nakamoto. In Bitcoin, the maximum total amount of distinct monetary units is therefore 2.1 quadrillion because of the pre-set cap of 21 million bitcoin. In higher layer applications, such as Lightning, bitcoin transactions can be denominated in fractions of a satoshi. When settled back on the Bitcoin blockchain however, a satoshi is the smallest functional unit available.