Organic Photochemistry is one of the most rapidly growing area of chemical sciences. Many organic compounds can be prepared photochemically on exposure to utraviolet or visible radiations of suitable wavelength, which is not possible otherwise by ordinary chemical reactions. Nature is also utilizing Sunlight for driving some photochemical reactions, which are useful for the life on the planet - Earth e.g. Photochemistry of Vision, Photosynthesis, etc. Such reactions are some times Stereoselective and/or Stereospecific in nature. The photochemistry of Olefins, Carbonyl Compounds and Aromatics play an important role in the synthesis of a number of compounds with desired structures and properties. Apart from synthetic uses of Photochemical reactions, they are also harmful in number of cases like Photochemical formation of smog, Photodegradation of Polymers/ Biopolymers, Photodynamic damage by Singlet Oxygen, In this book, an atempt has been made to make it equally useful for both, the beginners as well as the teachers.