Lakowicz has written a full-color, third edition of his classic textbook and reference, Principles of Fluorescence Spectroscopy, hereafter called Principles, that is easily understandable to students, scientists, engineers, and clinicians; specifically those individuals who have not studied physical chemistry (quantum chemistry, molecular spectroscopy, statistical mechanics, and kinetic theory) nor organic chemistry, and nevertheless are working with fluorescence techniques and optical microscopes, analytical instruments, diagnostic devices, or are developing new techniques based on these devices. I found the book to be eminently suitable for its intended audience. Lakowicz has extensive experience in fluorescence spectroscopy; he has taught the materials contained in the Principles, and he and his students and colleagues have made many significant contributions to the field. The well-tested and targeted audience-accepted approach is to teach the principles in a phenomenological manner that combines a concise, yet physically correct, qualitative exposition with carefully designed and executed multicolor diagrams, figures, and tables that contain experimental data. When necessary, the author provides the required equations that describe the phenomena. Furthermore, the author has designated advanced topics, which may be left out of the syllabus for an introductory course.