I received my Ph.D. in Biophysics from the Instituto Venezolano de Investigaciones Cientificas and my post-doctoral training at Harvard where I am now Professor of Cell Biology. Our research focuses on the processes that mediate and regulate the movement of membrane proteins throughout cells. In particular our studies have help define molecular mechanisms that underlie the cell's sorting machineries mediated by the clathrin pathway, the principal route responsible for receptor-mediated endocytosis and for secretion, a route critical for reuptake of membrane at synapses, and a mode of entry usurped by many viral and bacterial pathogens. These biological phenomena have importance for the understanding of such diseases as cancer, viral infection and pathogen invasion, Alzheimer's, as well as other neurological diseases. We also study how during cell division, cells control their size and organelle architecture. Our work has been characterized by use of emerging technologies -- from the early days of molecular cloning to contemporary live-cell imaging. We use the tools of x-ray crystallography, NMR, electron cryomicroscopy, and single-molecule biophysics to create a "molecular movie" of clathrin-mediated endocytosis, and in this way relate these molecular events to functional properties of the surfaces of living cells. We have helped defined the structure, interactions, and assembly-disassembly mechanisms of clathrin and many of its associated proteins, through studies extending over three decades, including the first X-ray crystal structure determination of clathrin and the AP-1 endosomal clathrin adaptor, and the first high resolution cryo-electron microscopy of a complete clathrin coat. We also use frontier optical-imaging modalities including super-resolution total internal reflection fluorescence microscopy and lattice light sheet fluorescence microscopy with single molecule sensitivity. Our fluorescent high resolution imaging microscopy techniques are geared to gather in 3D and real time, quantitative, “single-molecule” and "single-object" data to examine cellular membrane remodeling processes from in vitro reconstituted systems or from living cells. Focusing on clathrin-coated pits and coated vesicles, for example, we tracked them while they are assembling, recruiting cargo, membrane scission, budding and uncoating. The fluorescent probes include clathrin, AP-2, auxilin, dynamin and other molecules expressed in gene-edited cells as well as fluorescently tagged cargo. With these type of studies we integrate molecular snapshots obtained at high resolution with real time in vitro and live-cell processes, to generate ‘molecular movies' aimed towards obtaining new frameworks for analyzing some of the molecular contacts and switches that participate in the regulation, availability, and intracellular traffic of the many molecules involved in signal transduction, immune responsiveness, lipid homeostasis, cell-cell recognition and organelle biogenesis.