Have you ever seen images of tiny fish swimming peacefully next to hungry sharks? Or tiny birds sitting on the backs of huge rhinoceroses? These animal relationships, while hard to believe, are examples of symbiosis. In nature, many animals, plants, and other organisms form alliances that the benefit of at least one partner. Well-known science writers Alvin and Virginia Silverstein and Laura Silverstein Nunn explore the importance of symbiosis to all levels of life, including human beings. From parasites to protector-type relationships, and from under-the-sea to outer space locations, the authors investigate numerous instances that show just how creatures depend on each other for health and survival.