The field of heterogeneous photocatalysis has given rise to thousands of papers, typically dispersed across many journals. Consequently, from time to time, there is a need for a book providing information concerning the different facets of this field in a handy way. Actually, the present book includes both retrospective analyses and suitable examples of diverse aspects of the current research. It thus covers several basic aspects (photon absorption, active species/mechanisms/reaction pathways, efficiency evaluation), information on UV and visible-light sensitive photocatalysts and the relationship between their characteristics and the photocatalytic efficiency, critical reviews and articles on the potential of photocatalysis (and photoelectrochemistry) for decontamination (of air, water and surfaces) and for the production of energy and chemicals. The contributions have been written by well-known authors forming an ensemble whose excellence has rarely been matched in previous books on this topic.