The brain’s abilities are derived from the diversity and complexity of its neurons. We have recently mapped out a near-complete census of neural diversity in the retina, where vision begins. My group now seeks to understand the early development and evolution of neural diversity through a combination of experiment and statistical genomic analyses. I will describe efforts to reconstruct diversification of 45 distinct types of mouse retinal ganglion cells. We have recently analyzed the conservation of retinal neurons in 18 vertebrate species to build a quantitative understanding of how neuronal types are lost, gained or modified to suit the retina of each species to its visual needs. Excitingly, we find that neuronal types thought to be unique to primates (and therefore difficult to study and clinically important) may indeed have clear counterparts in many other species, including mice.