Photobiology is the scientific study of the interactions of light and living organisms. The last decades have witnessed great strides in understanding the biological effects of light from the molecular all the way up to the whole organism level. Much of the boost for advancing the science of photobiology came from the dramatic increase over this period in the incidence of melanoma and other sun-related skin diseases. In this book, current knowledge about the risks of ultraviolet radiation (UVR) on infant skin are summarised, including epidemiologic evidence regarding sun exposure in this age group. This book also explores and discusses the complex cascade of modifications induced within proteins through exposure to irradiation. Exciting new approaches to the characterisation, location, tracking, and ultimately control of photoxidation within proteins are discussed as well. Moreover, the prevention for phototoxic effect is one of the important themes of photobiology. The chemopreventive action of novel organic and inorganic materials on photosensitised biomolecules damage is described in this book. Other chapters provide insights into the death and protective responses of cells treated by photodynamic therapy (PDT) as well as the relationships among gene expressions, examine the effects of natural ultraviolet radiation at zooplankton populations and communities in inland water ecosystems, and the application of folates and their role for skin homeostasis.