The air that enters our lungs when we breathe in contains oxygen, which our bodies need to help turn food into energy. When we breathe out, carbon dioxide is removed from the body as a waste product. In this informative book, readers learn how the respiratory system works as well as its parts and their structure. The main content, sidebars, and fact boxes explain the science in accessible language and age-appropriate detail as well as cover illnesses that can damage the system and how to maintain healthy lungs. Full-color photographs and diagrams aid readers' understanding.