The recent development of programmable nucleases has the potential to revolutionize biological sciences. In particular, the Cas9 nuclease, which functions as a component of the clustered regularly interspaced short palindromic repeats (CRISPR) system in bacteria, has proven to be a highly efficient tool for genome editing in a wide range of model organisms, including mouse, zebrafish,Drosophila, and Caenorhabditis elegans. Application of Cas9 also allows straightforward genetic manipulations in cultured cells and is efficient enough to perform genome-wide screens in cell lines. However, applying genome editing tools in this manner in vascular biology is challenging because of the widespread use of primary cell cultures, which have a limited lifespan and are difficult to use for clonal analysis. Fortunately, studies by Abrahimi et al in this issue describe several solutions that facilitate the application of Cas9 in cultured endothelial cells. Together, these technical advances provide a valuable platform to enable straightforward and robust reverse genetic analysis in endothelial cells.