Interkinetic nuclear migration (INM), the movement of neuroepithelial and radial glial cell nuclei along the apical-basal axis in concert with the cell cycle, underlies the pseudostratification of the ventricular zone (VZ). Recent studies provide insight into the molecular mechanisms of INM and its effects on neural progenitor cell fate determination. Moreover, INM not only has a key role in increasing the VZ progenitor pool, but also may have set the stage for the evolution of subventricular zone progenitors implicated in cortical expansion.