Since the dawn of time, people have noticed that members of families tend to look alike, having similar hair or eye color, for instance. Similarly, ancient farmers and herders realized that if they mated, or bred, plants or animals with desirable traits (such as the ability to grow quickly or resist disease), they had a better than average chance of obtaining offspring with those traits. Still, the actual science of genetics and genetic engineering is only about 100 years old. Many genetic engineers and biologists have contributed to new understandings of heredity and the ways genes can be manipulated to stimulate certain characteristics in living things. "Modern Genetics" profiles 14 men and women who were among the leaders in making important genetic discoveries in research and new technologies. Profiles include James Watson, Francis Crick, Herbert Boyer, Stanley N. Cohen, Michael Bishop, and Harold Varmus.