Cargo proteins moving between organelles are transported by membrane-enclosed vesicles. The core engines mediating vesicle trafficking are now well established. However, we areonly beginning to understand the regulatory networks superimposed upon the core engines to adjust the rate and direction of membrane transport according to physiological demands. The advent of the revolutionary CRISPR-Cas9 genome editing system enabled us to systematically identify new components of the regulatory networks. We developed new screening platforms and performed unbiased genome-wide CRISPR genetic screens to dissect the exocytosis and endocytosis of cell surface transporters, fundamental processes in cell physiology. Our screens identified known regulators but most of the hits were not previously known to regulate the pathways. I will focus on the unexpected mechanisms of RABIF/MSS4 in exocytosis and AAGAB in endocytosis. I will also discuss how the principles uncovered in our studies shed light on vesicle trafficking in general.