One of the triumphs of modern science has been our ever-improving understanding of how life works—how chemical reactions at the cellular level account for respiration, digestion, reproduction, locomotion, and a host of other living processes. This exciting subject is biochemistry—and its allied field of molecular biology. In the past century, progress in these complementary disciplines has been astonishing, and a week rarely passes without major advances in medicine, physiology, genetics, nutrition, agriculture, or other areas, where biochemistry and molecular biology are shedding new light on life.