Since Wilhelm Roentgen's accidental discovery of x-rays in 1895, scientists and doctors have been fascinated by the possibilities of radioactivity. Early on, the importance of radiation protection became clear as health effects from radiation exposure were observed, and in the 1940s, the field of health physics was born at the University of Chicago's Metallurgical Laboratory. Herbert Parker, one of the first health physicists, developed some of the first health physics programs as part of the Manhattan Project. This guide provides resources that cover the history, principles, and practices of radiation safety and health physics.