Genetic screens are one of the most potent unbiased tools to identify gene functions. Following pioneering studies of whole genome gene deletion studies in yeast, CRISPR/Cas9 pooled genome-wide KO screens now allow similar screens to interrogate directly the genetics of human cell lines. When made in the presence of bioactive compounds affecting growth (chemogenomic screens), the genes whose knockout are deleterious to growth (sensitizers or synthetic lethals) or favor growth (rescues or s...