The cells of our bodies are surrounded by a membrane that separates the molecules inside the cell from those on the outside. This membrane barrier provides cellular identity, and is essential for life as we know it, but it also represents a problem. How are large molecules that the cell needs to survive internalized? Likewise, how can the composition of the membrane be controlled to optimize the interaction of the cell with its environment? These fundamental issues of cellular function are solved in part by membrane traffic, the regulated movement of regions of membrane and their associated macromolecules using small carriers called vesicles. Our laboratory focuses on elucidating the underlying mechanisms that control these trafficking pathways in vivo.