Students watch the human heart in action, learn how muscles and bones work, and more—with involving books coordinated to our Learning Science Activity Tubs - Grades 4-6. Our skill-building library features 5 fascinating books that reinforce and expand on the themes presented in our Human Body Activity Tub…with wonderfully illustrated, high-interest titles that make concepts super-easy to grasp. You get a set of 5 paperback books.