The article reviews the recent findings that some glial cells, specifically radial glia (RG) in development and certain astrocyte subpopulations in adult mammals, function as primary neural stem cells (NSCs). This challenges the classical view that neuronal and glial lineages diverge early in development. The behavior of NSCs and lineage-tracing studies reveal how neuronal lineages emerge. Many neurons and glial cells are not directly derived from NSCs but from intermediate progenitor cells (IPCs). The timing and location of NSCs, linked to their neuroepithelial origin, are key determinants of the types of neurons generated. The identification of NSCs and IPCs is crucial for understanding brain development, adult neurogenesis, and brain repair strategies. The article also discusses the transformation of neuroepithelial cells into RG, interkinetic nuclear migration (INM) in RG cells, asymmetric divisions of RG cells, the role of Notch signaling in SVZ IPCs, and the persistence of RG in some vertebrates as primary progenitors of new neurons. Additionally, it explores the nature of NSCs in the adult subventricular zone (SVZ) and the potential markers for identifying these cells.The article reviews the recent findings that some glial cells, specifically radial glia (RG) in development and certain astrocyte subpopulations in adult mammals, function as primary neural stem cells (NSCs). This challenges the classical view that neuronal and glial lineages diverge early in development. The behavior of NSCs and lineage-tracing studies reveal how neuronal lineages emerge. Many neurons and glial cells are not directly derived from NSCs but from intermediate progenitor cells (IPCs). The timing and location of NSCs, linked to their neuroepithelial origin, are key determinants of the types of neurons generated. The identification of NSCs and IPCs is crucial for understanding brain development, adult neurogenesis, and brain repair strategies. The article also discusses the transformation of neuroepithelial cells into RG, interkinetic nuclear migration (INM) in RG cells, asymmetric divisions of RG cells, the role of Notch signaling in SVZ IPCs, and the persistence of RG in some vertebrates as primary progenitors of new neurons. Additionally, it explores the nature of NSCs in the adult subventricular zone (SVZ) and the potential markers for identifying these cells.