How many cells does your skin shed every minute? Why can walking through a doorway make you forget things? Which grow faster — your fingernails or toenails? Find the answers to these questions and many more in this fact packed book. From the smallest cells to the largest bones, explore the human body, inside and out. On the journey to becoming a human body expert, take quizzes, earn a special certificate, and then use the included press-out pieces to build your very own human skeleton model!