The "subprime mortgage crisis" in the United States began to appear gradually in the spring of 2006. In August 2007, it swept the major financial markets in the world, such as the United States, the European Union and Japan. Since August 2007, the Federal Reserve has increased market confidence by injecting liquidity into the financial system, and the US stock market has remained at a high level. It seems that the situation is not so bad.
However, in August 2008, the share prices of Fannie Mae and Freddie Mac, the two mortgage giants in the United States, plummeted, and financial institutions holding Fannie Mae and Freddie Mac bonds suffered huge losses. The US Treasury and Federal Reserve were forced to take over Fannie Mae and Freddie Mac to show the government's determination to deal with the crisis.
References:
Baidu encyclopedia-subprime mortgage crisis