If you ride a bicycle or a skateboard, or if own roller skates, you use wheels and axles. Readers discover the science behind these important simple machines. It's hard to go anywhere in our world today without seeing wheels and axles at work. Cars and trucks use these to take people to work and school every day. Tractors and wagons on farms have wheels and axles, too. Manageable text and vivid photographs help readers understand this basic science topic. A comprehensive glossary and a useful graphic organizer accompany the concepts presented, which aid readers in navigating this fun and fact-filled book.