Hsien-Hsin Tung, PhD, was a senior investigator in Pharmaceutical Research & Development for Merck Research Laboratories until his retirement. Dr. Tung founded the Crystallization Laboratory in Chemical Engineering Research & Development, Merck Research Laboratories. Edward L. Paul, PhD, is retired director of Chemical Engineering Research & Development at Merck Research Laboratories. In addition to numerous patents and publications, Dr. Paul was coauthor of several chapters in, and senior editor of, the Handbook of Industrial Mixing: Science and Practice (Wiley). Michael Midler, PhD, is retired senior investigator, Chemical Engineering, with Merck Research Laboratories. His more recent patents and publications are primarily in processes for crystallization and the mixing of liquids. Dr. Midler coauthored, with Dr. Paul, "Mixing in the Fine Chemicals and Pharmaceutical Industries," in the Handbook of Industrial Mixing: Science and Practice. James A. Mccauley, PhD, was a senior investigator in the Analytical Research Department for Merck Research Laboratories until his retirement. After that, he served as an adjunct professor for the Pharmaceutical Engineering Training Program in the Department of Chemical and Biochemical Engineering at Rutgers University.