The risks encountered by financial centers can also be called financial crisis. Financial centers are based on virtual economy, so common crises such as banking crisis, real estate crisis and stock market futures crisis are mainly in these three aspects (stock market and futures are closely related, but only one aspect). The most typical example is the subprime mortgage crisis in the United States in 2008, which spread from real estate to banking, and then dragged down many economies around the world. It is a combination of real estate and banks.