A teeter-totter is more than fun to play on, it's also a lever, one of the six simple machines. This accessible book introduces readers to the lever through real-world examples. They'll learn about simple and more complex inventions using the lever that have changed the world. Detailed pictures with thorough annotations explain important engineering concepts. Cool "Technology in Action" spreads let readers get a close-up look at levers at work. This accessible text introduces readers to important STEM concepts and encourages an interest in engineering.