It is now possible to describe—imperfectly, but in more than outline—the types of neurons by which the retina carries out its computations. This is the rough draft of a “neurome,” a conscious effort to list all the tissue’s neurons. Identifying the cell populations has led directly to a revised conception of the retina’s input–output functions and of the fundamental elements from which visual perception is built. The retina is the first substantially complex structure of the central nervous system for which such a more or less complete parts list is available (Fig. 1). The resulting picture, the work of a community of investigators worldwide, resulted in a paradigm shift. A retina once imagined as based around a 6-to 12-cell module was replaced by a retina of multiple parallel arrays, containing at least 60 functionally different cell types and decomposing the visual input into more than a dozen different representations. The multiplex structure raises fundamental questions about the events that must occur later, in the central visual system.

Here, I will give a global view of the retina’s cell populations, aimed, like the Proctor Lecture itself, at an audience of nonspecialist vision scientists. I will review how the cell populations were revealed and how they participate in the retina’s functions. Along the way, I will point out some of the places where our concepts of the retina were overturned and comment on the next generation of questions.