Here's the first paper I've selected as Brad's Paper of the Day. The authors use elegant screens in bacterial and mammalian cells to improve the on-target efficiency of cytosine base editors. For those who haven't been following CRISPR\/Cas9 technology, base editors employ an engineered fusion protein comprising cytidine deaminase linked to a Cas9 nickase protein and multiple copies of a uracil glycosylase inhibitor (UGI). When the synthetic editor complex is directed to a target C·G base pair by an sgRNA, it is converted to a T·A base pair. The screens used by the Liu lab resulted in optimized base editors with 10- to 100-fold reduction in off-target editing.