Continuing his journey through the human body, Simon (The Brain, 1997, etc.) presents muscles in living color, with dramatic close-up and computer-imaged photographs. Readers learn about three common muscle types: skeletal, the striated kind; smooth muscles, found lining the stomach and intestines; and the unique cardiac muscle, the heart. Describing each type of muscle, its appearance, location, and function, Simon surprises readers with the facts--that muscles make up 40 percent of human body weight, that each muscle is a single cell, and more. While the captions do not explain the degree of magnification used in the photography, the pictures invite readers to explore statements in the text, i.e., the striation of voluntary muscles compared to involuntary muscles, or the proximity of the diaphragm to the rib cage.