The stablecoin, known as USDD, was developed by a Chinese blockchain company called USD Digital. It is backed by a basket of fiat currencies, including the US dollar, the euro, and the Japanese yen, among others. The stablecoin is pegged to the value of these fiat currencies and is designed to maintain a stable value, hence its name.

Stablecoins are becoming increasingly popular in the cryptocurrency market, as they offer a stable and reliable alternative to the volatility of other cryptocurrencies like Bitcoin. They also allow traders to avoid the fees and delays associated with transferring fiat currencies between exchanges.

The investment by KuCoin and Circle in USDD is a significant endorsement of the stablecoin's potential. It is also a sign of the growing interest in stablecoins in China, which has been cracking down on cryptocurrencies in recent months.

The Chinese government has been tightening its grip on the cryptocurrency industry, banning initial coin offerings (ICOs) and cryptocurrency trading in 2017. In recent months, it has also banned cryptocurrency mining and trading platforms.

Despite this, stablecoins have been able to gain a foothold in China, as they are seen as a more stable and reliable alternative to other cryptocurrencies. USD Digital's USDD is one of the most popular stablecoins in China, with a market cap of over $800 million.

The investment by KuCoin and Circle in USDD is expected to help the stablecoin expand its reach even further. It will also provide more liquidity for the stablecoin, making it easier for traders to buy and sell USDD on exchanges.

In a joint statement, KuCoin and Circle said: "We believe that stablecoins have a critical role to play in the future of digital currency. We are excited to be investing in USD Digital and look forward to working with USD Digital to further the development and adoption of stablecoins in China and beyond."

The investment by KuCoin and Circle is just the latest sign of the growing interest in stablecoins in the cryptocurrency market. As the market continues to mature, stablecoins are likely to play an increasingly important role in providing stability and liquidity to traders and investors alike.