This article discusses the design mechanisms, historical development, and risk assessment of stablecoins, analyzing the operational principles and trade-offs of three main types: fiat-backed, multi-asset collateralized, and synthetic dollar models. This article is based on a piece by ARK Invest and is organized, translated, and authored by Block unicorn. (Previously: after the xUSD stablecoin depegged, the USDX pool also dried up) (Background: Balancer: V2 pool suffered a loss of 128 million from a vulnerability attack, V3 remains unaffected; experts criticize: auditing dozens of times is fundamentally useless) This article aims to explain the complex mechanisms in the stablecoin space. The operational mechanisms of stablecoins are quite complicated, and there are currently no comprehensive educational resources that can integrate the mechanisms, risks, and trade-offs of various stablecoins. This series of articles aims to fill this gap. The series consists of four parts, with the first part introducing stablecoins, including their design and history. The remaining three articles will follow.