The U.S. subprime mortgage crisis in 2008 caused a big financial problem. Banks were worried about losing money, so they stopped lending to each other. This made it hard for people and businesses to get loans. To fix this, central banks gave money to banks and lowered interest rates. The crisis started when interest rates were low, making it easy for people to buy homes. But as rates went up, many couldn't pay their mortgages. Banks sold risky mortgage debts to other investors, which made the problem worse. As more people couldn't pay their mortgages, housing prices fell, and more loans went bad.