Muscles are like the body's movers and shakers, helping you do everything from smiling to jumping. They're made up of tiny fibers that act like a team when you want to move. When you tell your muscles to do something, special chemicals signal them to contract, like pulling on a rope. This contraction makes your muscles shorten and creates the movement you asked for. So, muscles are like your body's super-responsive helpers, always ready to spring into action when you need them!