This book discusses the most important classes of heterogeneous catalysts with a systematic approach in which the design of each catalyst is rationally explained. Although heterogeneous catalysts are complex systems, it is possible to discuss them based on two terms: (1) Which are the active sites? (2) Which is the optimum structure for this type of catalyst? Following this approach, the book provides a unique resource for understanding how heterogeneous catalysts operate and stimulate the inspiration of researchers in designing novel heterogeneous catalysts. The book is a must-read for many researchers working with heterogeneous catalysts, both in academia and industry, and for graduate students in the field in chemistry, chemical engineering and materials science.