Vive la difference!

The subfields of the primate visual cortex differ in their cytological composition, including the relative width of the layers. In this issue of Neuron, Lukaszewicz et al. report that the origin of these laminar, and thus areal, differences can be traced to the kinetics of progenitor cell divisions in the subjacent proliferative zones that generate neurons that migrate radially to the appropriate layers at each side of the cytoarchitectonic border.