Neural stem cells can be isolated from the mouse embryonic cortex but do not persist in the adult cortex. In contrast, neural stem cells from the striatal embryonic germinal zone persist in the adult subependyma. Emx1-lineage analysis revealed that cortex-derived neural stem cells survive and migrate ventrally into the subependyma where they intermix with the host striatal neural stem cells [S. Willaime-Morawek et al. (2006)J. Cell Biol. 175, 159-168]. Cortex-derived cells proliferate faster in the subependyma and reach the olfactory bulb earlier than striatum-derived cells. In the olfactory bulb, cortex-derived cells produce more cells and more dopaminergic neurons in the glomerular layer than striatum-derived cells. Cortex-derived cells also give rise to more astrocytes and less neurons in the striatum than striatum-derived cells. Thus, history matters; cortex-derived neural stem cells in the subependyma give rise to progeny in the olfactory bulb and striatum but in different proportions than striatum-derived neural stem cells.