This mouse retina was electroporated with EphA4, an ephrin found perinatally in the retinal ganglion cell layer that has unknown roles in visual development. Shown are EphA4-expressing cell clusters (green) and retinal ganglion cell axons labeled with Tuj1 (red). Veronica Murcia-Belmonte and colleagues discovered that EphA4 from retinal ganglion cells interacts with ephrinB1 in medial regions of the superior colliculus, thereby promoting visual system connectivity. See the article by Murcia-Belmonte et al. for more information on how EphA4 contributes to visual development. Cover image: Yaiza Coca