The Federal Reserve's official website released the speech of Governor Waller "Reflections on the Maturing Stablecoin Market". He said that he defines a stablecoin as a digital asset that aims to maintain a stable value relative to the national currency. Like any means of payment, a stablecoin must have: a clear use case and a clear business case to be economically viable. The US dollar is the preferred fiat currency for most stablecoins, and in this sense, stablecoins are synthetic US dollars. The second use case for stablecoins is to provide a means to acquire and hold US dollars. The third use case is cross-border transfer. The industry is increasingly focusing on the "stablecoin sandwich" model of cross-border transfer. The last use case is retail payments. So far, most stablecoin issuers seem to generate revenue primarily by earning more from their reserve assets than they spend.