Understanding the biology of healthy skin and how it changes in disease is important for the development of new drugs to treat skin disease and for understanding and interpreting the effects of chemical exposure. Current developments in molecular medicine, use of in vitro models, in vivo imaging techniques integrated with clinical observation in dermatology are directed towards improving knowledge in this area. The chapters in this book section cover a wide range of such developing areas of biology and make a useful contribution to our current understanding of the biology of the skin.