Adult neural stem cells (aNSCs) primarily exist in two regions:the subventricular zone (SVZ) of the lateral ventricle (LV) and the subgranular zone (SGZ) in the hippocampal dentate gyrus (DG) [1].It has been revealed that aNSCs in the SVZ (called type B cells) originate from embryonic NSCs mainly before embryonic day 15.5 (E15.5),and are set aside for postnatal neurogenesis after diverging [2,3].Whether this is the case with aNSCs in the hippocampus remains to be resolved [4].A prominent new study by Hongjun Song and colleagues showed that dentate NSCs from embryonic to adult stages share a common early origin,suggesting that neurogenesis in the hippocampus is a continuous process throughout development [5].