Traditionally zoos were designed neither for people nor animals; barred cages taught people more about their separation from nature than about an animal and its habitat. But just as man has realized that he has all but destroyed much of the world's wilderness and its wildlife, he is realizing that the zoo may be the last refuge for wildlife. NOVA visits several United States zoos to examine a variety of activities of concern today: breeding, public education, creative new animal habitats, and the reintroduction of animals to their natural environment.