The development of genetically engineered proteins that can control cell excitability with light have revolutionized our understanding of the nervous system. The most widely used of these optogenetic tools is the light-gated ion channel, channelrhodopsin 2 (ChR2). A new study by Cho et al. describes the development of ChR2 variants with improved photocurrents and more selective ion permeability using an automated multifaceted fluorescence-based screening. This methodological framework holds promise not only in refining features of ChR2, but also for other proteins in which fluorescence phenotyping is possible.