Robinhood Markets (NASDAQ:HOOD) has expanded its retail-focused cryptocurrency offerings through the addition of USD Coin (USDC-USD) stablecoin, it said in a Twitter post Tuesday.Users will be able to transfer USDC, the second-largest stablecoin by market cap, on both Polygon (MATIC-USD) and Ethereum (ETH-USD) networks starting Wednesday.Johann Kerbrat, the company's chief technology officer, said earlier that he will talk more about what this move means for HOOD and what will come next during next week's Converge22 conference in San Francisco.Of note, a stablecoin is a digital token in which its value is tied to a reference asset such as a fiat currency like the U.S. dollar or a commodity like gold.Earlier this month, (Sep. 9) Robinhood said it's working on making cardano transfers available on its crypto platform.