Graça Raposo1, Philip D Stahl2. 1. Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique UMR144, Structure and Membrane Compartments, Paris, France. graca.raposo@curie.fr. 2. Department of Cell Biology, Washington University School of Medicine, St Louis, MO, USA. pstahl@wustl.edu.