The Lightning Network is a system of bi-directional payment channels that enables users to securely send fast, low-cost cryptocurrency payments. Lightning gained initial traction with Bitcoin as a layer 2 scaling solution by enabling efficient micropayments and instant transactions, which allows Bitcoin to function more effectively as a medium of exchange. The network's design builds on earlier work in payment channel development, utilizing cryptography to trustlessly route payments in an off-chain network without counterparty risk. This approach mitigates the scalability constraint of a fixed block size. While the Bitcoin Lightning Network is most established, other cryptocurrencies such as Litecoin and Decred are also implementing versions.