Fish catch color with rods Vertebrates are typically thought to have a consistent system for processing light, in which multiple cone opsins permit color vision during the day, but a single rod opsin provides only monochrome vision in the dark. Musilova et al. analyzed more than 100 deep-sea fish genomes and found a previously unknown proliferation of rod opsin genes that generate rod opsin photopigments that are tuned to different wavelengths of light. These receptors may allow the fish to perceive bioluminescent signals that pervade their deep-sea environment. These results reveal a previously undescribed visual system that allows for color vision in the dark. Science , this issue p. 588