What is in chocolate that makes us feel good when we eat it? Which natural drug protects the heart? What is Nature's sleeping pill? What radioactive lifesaver should be in every home? And what is the clean, cold fuel for the coming century? The answers to these and to very many other intriguing questions are to be found in John Emsley's Molecules at an Exhibition, a portrait gallery featuring materials that affect every aspect of our daily lives. The collection ranges widely. There is a portrait of selenium, which prevents certain types of heart condition and is of use to the body in warding off cancer; a rich source is the Brazil nut. There is one of folic acid, which protects babies in the womb, and one of arachidonic acid, a lack of which can be a serious problem for premature babies. There are galleries devoted to the home, to the environment, and to materials that make life a little easier for us. And in a rogues' gallery there are molecules that can harm or kill us. This book is intended for the general public, particularly those who are concerned about food, health, and the environment.