Unlocking retinal regeneration in mice: Zebrafish can regenerate damaged retinal tissue, but mice cannot. Hoang et al. found that tracking changes in gene expression and chromatin accessibility upon injury revealed clues as to why retinal glial cells in zebrafish could generate new neurons but the same cell type in mice could not. In zebrafish, activated Müller glial cells shift into a proliferative phase, whereas in mice, a genetic network returns the glial cells to quiescence. A few transcription factors enforce quiescence in the mouse, and disruption of these allowed Müller glia to proliferate and generate new neurons after retinal injury. Science , this issue p. eabb8598