Your body is made up of tiny cells that combine to make tissues. When two or more tissues join together to perform a specific function, it is called an organ. Organs work within various systems to regulate your body's functions. Your stomach helps digest food, your heart pumps blood to all parts of your body, and your skin protects you from dangerous microbes. From the brain to the bladder, each of your organs performs an important job that is necessary for you to live.