In this episode of "THE BODY," we look at fat and muscle, organs whose importance is often misunderstood. Many people believe that fat simply stores energy and muscles just move the body. However, recent research has revealed that both organs have an unimaginable variety of functions. They discharge special substances that transmit vital messages throughout the body, manipulating desire, affecting immune function, enhancing memory and even fighting cancer. Using the latest research, we'll explore how their surprising power can protect us from deadly disease.