This is a practical guide to the inner workings of things we see around us and machines we use all the time. Following the format of the Eyewitness Science Guides series, the book shows experiments that engage the reader directly with the subject. Step-by-step photographs and instructions devised by expert consultants guide the reader safely through the experiment. By building working models of objects and carrying out experiments, children and adults can immediately see how things work. Text accompanies detailed, cut-through illustrations, and special features contain details about famous inventors and inventions. The book builds up a picture of the complex technological world we live in by describing a wide range of objects, from personal items such as pens to largescale structures such as bridges.