How do checks and balances work in the government and give example?

One famous example happened just before the US Civil War. The US Congress the legislative branch passed a bill called the Kansas-Nebraska Act of 1854. The US president, the head of the executive branch signed the bill into law and as the executive branch does, it must enforce the law. Two branches of the Federal government used their powers to create this particular law. In 1857, the US Supreme Court, the judicial branch of the Federal government, exercised its power to check the other two branches by deciding the Act was unconstitutional. Here is an example of how two branches of government can be checked in balance by another one.