This booklet is one of the "Understanding the Atom" Series. The science of spectroscopy is presented by a number of topics dealing with (1) the uses of spectroscopy, (2) its origin and background, (3) the basic optical systems of spectroscopes, spectrometers, and spectrophotometers, (4) the characteristics of wave motion, (5) the electromagnetic spectrum, (6) types of spectra, (7) line spectra, and (8) interpretations of spectra information. In addition, there is a discussion of the fundamental concepts of quantum mechanics, the origin of spectra, and of the different kinds of spectroscopic techniques including x-ray spectrography, mass spectrometry and infrared, fluerescence, magnetic, Raman, and electron spin resonance spectroscopy. References to popular books, technical books, and journal articles are provided. (LC)