Textbook in PDF format Understanding the nature of light is a fundamental question that has troubled mankind since antiquity. It took a great deal of speculation and study concerning the formation of the rainbow to formulate the right hypotheses to explain the iridescence observed when white light passes through raindrops or pieces of glass. For a long time, ancient philosophers were far more interested in the propagation of the light than in its nature. A History of Spectroscopy retraces the major stages in the growth of the various spectroscopic methods from their origins, as well as the most recent advances and the hopes they raise for future technological progress. With its multidisciplinary aspects, it embodies a masterly and unique effort which has no equivalent in the published literature. The present contribution will be read with profit not only by students embarking on a career in physics in general and in spectroscopy or astrophysics more specifically, but also by students in many other related fields like chemistry, biology, medicine, pharmacy and engineering