Granule neuron maturation within the developing cerebellum. Different cellular layers within the maturing postnatal cerebellum are shown on the left: oEGL outer external germinal layer, PMZ pre-migratory zone, ML molecular layer, PL Purkinje cell layer, and IGL internal granule cell layer. On the right are different genes that are expressed during specific stages of CGN maturation, with their developmental expression indicated by solid vertical bars (variable bar intensity indicates relative extents of expression for a given gene during development)