The Human Body presents information and investigations on these nine concepts: Cells are the fundamental unit of life.* Specialized cells protect the body from harmful substances.* Food follows a path as it is digested.* Good nutrition provides energy for cell growth and repair.* The heart and lungs work together.* Muscles and bones provide movement and support.* The nervous system relays messages to and from the brain.* Parents pass traits to future generations.* Body systems interact.