The branch of chemistry which is concerned with the chemical effects of lights is known as photochemistry. It generally deals with chemical reactions that are caused by the absorption of ultraviolet, visible light and infrared radiation. The most common photochemical reactions include bioluminescence, photoresist, photosynthesis, vision, toray, photodegradation and photodynamic therapy. Some of the major concepts and laws within this field are Grotthuss–Draper law, Stark-Einstein law, Kasha's rule and Hund's rule of maximum multiplicity. There are various areas of study within this field such as organic photochemistry, inorganic photochemistry and organometallic photochemistry. This book unfolds the innovative aspects of photochemistry which will be crucial for the progress of this field in the future. Those in search of information to further their knowledge will be greatly assisted by this book. Coherent flow of topics, student-friendly language and extensive use of examples make it an invaluable source of knowledge.