Thomas D. Pollard, MD, Sterling Professor, Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, William C. Earnshaw, PhD, FRS, Professor and Wellcome Trust Principal Research Fellow, Wellcome Trust Centre for Cell Biology, ICB, University of Edinburgh, Scotland, United Kingdom and Jennifer Lippincott-Schwartz, PhD, Group Leader, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, Virginia, United States