In May 2024, the Bitcoin (BTC) halving will be one of the hottest events in the market. As the halving approaches, more funds will focus on Bitcoin, drawing investor attention to the Bitcoin-derived ecosystem. Layer 2, with its compelling narrative, is likely to become a preferred target for alpha-seeking capital. This article provides an overview of the current BTC Layer 2 concept race and introduces representative projects, including Stacks, RSK, and the Lightning Network.