Among great technologic developments of the twentieth century has to be that of laser light with its myriad of applications in industry, communication, medicine and many other fields. As author Hal Hellman says in conclusion in this 1968 publication, “Indeed the most exciting probability of all is that lasers undoubtedly will change our lives in ways we cannot even conceive of now.” And, so has it been, and this treatise gives insight into the early days of the research and development of lasers. This booklet is part of the Understanding the Atom Series from the United States Atomic Energy Commission Division of Technical Information.