Human technology has taken 10,000 years to develop; natures mechanical designs are billions of years old. Both technologies share the same physical environment but produce vastly different results. Human designers love right angles, but nature is typically rounded and its angles are diverse. We use wheels in numerous ways, yet nature's only true wheels lie in bacteria. We prefer to make surface ships, while nature swims. Our hinges turn because their parts slide, whereas natural hinges (such as a rabbit's ear) turn by bending their flexible materials. This book is about how the ways of living things work and how they grow. It introduces the reader to the field of biomechanics and explains how physical law and historical accident determine the designs of both people and nature.