Pao K. Wang is a Professor in the Department of Atmospheric and Oceanic Sciences, University of Wisconsin, Madison, where he has been teaching and conducting research for more than 30 years. He has won many recognitions for his contributions in atmospheric science including the Alexander von Humboldt Award, an S. C. Johnson Distinguished Fellowship and election as a Fellow of the American Meteorological Society and the Meteorological Society of Taiwan. Professor Wang has been the principal investigator of numerous research grants sponsored by NSF, EPA, NASA and DOE, covering topics in cloud physics, cloud dynamics, aerosol physics, air pollution and historical climatology. He is an associate editor of Atmospheric Research and European Journal of Physics-Plus, a member of the international advisory board of Terrestrial, Atmospheric and Oceanic Sciences and is also currently an advisory committee member of the Research Center for Environmental Change (RCEC), Academia Sinica, Taiwan.