Muscle is the tissue of the body which primarily functions as a source of power. Muscles are classified as striated muscle and smooth muscle. Striated muscle is further classified as skeletal muscle and cardiac muscle. Muscle which is responsible for moving extremities and external areas of the body is called skeletal muscle. Heart muscle is called cardiac muscle. Fibers are long and parallel without branching in skeletal muscle. Cells are joined together end to end by cell junctions forming the intercalated disks in cardiac muscle. Smooth muscle does not exhibit striations. Clinical images are also provided in the chapter.