Following a description of the structure of the atomic nucleus, the author describes the several kinds of nuclear instability and their consequences: alpha, beta and gamma emission. He then outlines the actions of these types of radiation and their biological effects, andexplains the uses of radiation and radioactivity in engineering, science and medicine. Next, he describes nuclear fission and how nuclear reactors produce nuclear power, and finally, he discusses nuclear fuel waste, with detailed descriptions of its disposal chemistry. A chapter on the various nuclear accidents that have occurred in the past leads into a thought-provoking section on whether or not we have learned enough to be sure that we are safe today.