Many of the early cloud chemistry studies were motivated by understanding acid rain and therefore were focused on the aqueous-phase production of sulfate. Peter Hobbs and the Cloud and Aerosol Research Group at the University of Washington played an important role in these investigations. Since those times, advances in cloud chemistry include the role of cloud physics in affecting aqueous-phase chemistry. Examples of this interaction are the dependence of sulfate production on the drop size distribution and the role of the ice physics in enabling the washout of soluble species. More recently, the importance of organic aqueous-phase chemistry in the production of secondary organic aerosol mass has been recognized. Because the organic aerosol is ubiquitous and abundant, the role of organic aqueous chemistry in contributing to organic aerosol mass must be assessed.