Phototherapy, the use of light to treat a variety of conditions, is not new and has been researched for well over 100 years. It has mainly been confined to ultraviolet wavelengths for its antibacterial properties. With the advent of LASER and Light Emitting Diodes, treatment in the visible spectrum and its fringes has gained credence both from research and through anecdotally reported results. This book aims to look at its application along with the theory and science underpinning its use in clinical practice. It will also suggest some explanations of how cellular structures are directly affected.