The definition of photomorphogenesis, is any change in form or function of an organism occurring in response to changes in the light environment. Photomorphogenesis is often defined as light-regulated plant development , but there are also changes in morphology and/or cell structure and function, which occur as transient acclimatizations to a changing environment, which are also light regulated. Particularly if this more inclusive definition is used, photomorphogenesis is a process common to organisms well beyond the plant kingdom. While there may be only a few examples of photomorphogenesis in the animal kingdom, it is a common feature of development in fungi, protists, and bacteria, as well as plants. The book is designed primarily to be used as a resource book for new researchers in plant photobiology.