The discovery and development of catalysts has placed played a major role in advancing technologies for the production of fuels and chemical throughout the 20th century, as well as technologies for the abatement of air pollution from mobile and stationary sources. These advances have, in part, been aided by advances in understanding composition and structure of catalysts and how these properties relate to catalyst activity and selectivity. This knowledge has come as a result of using a wide variety of spectroscopic methods and electron microscopy, together with isotopic tracer methods and measurements of kinetics. Theoretical methods have also advanced to the level where they can provide meaningful insights into the relationships between the local structure of an active site and its activity and selectivity in promoting a targeted reaction. This talk will summarizes the advances that have been made in the field of catalysis and understanding catalytic processes from a molecular perspective and will outline the challenges and opportunities for future research.