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, as well as the realization that light plays an important role in skin aging. Due to the fact that many of these conditions occur late in life, little attention has been paid to the effects of light on infant skin, with the exception of the use of violet-blue light for the treatment of jaundice in newborns. However, mounting evidence shows that a history of early sun exposure may affect the development of sun-related conditions later in life. This book examines the effects of UVR on the biology of infant skin.