The third edition of the handbook has been reorganized and subdivided into nine sections, including several chapters written by different authors. It may seem to some as too many chapters, but the editors chose this format intentionally to guarantee that each subject be described by a recognized expert in his/her field who is well aware of the latest development in the topic. Also, authors were selected worldwide. Indeed, cosmetology is universal, but there exists some regional specificity, which had to be addressed.