Provides a short course into nuclear physics with emphasis on how radiation affects the human body. Explains the phenomenon of hormesis whereby small doses of a substance or other agent that is poisonous in large amounts is beneficial in small doses. Recounts the better health statistics of the Japanese that were exposed to atomic bomb radiation as compared to unexposed peers. Discusses over 150 peer reviewed studies showing that low doses of radiation increase the longevity and health in animal and human studies. Shows conclusively that low dose radon exposure in homes in not dangerous, but therapeutic.