The adult mammalian brain retains neural stem cells that generate new neurons in two restricted regions: the subventricular zone (SVZ) and the dentate gyrus subgranular zone (SGZ). These niches, which are spatially isolated and serve different brain systems, share common features: astrocytes function as both stem cells and niche cells, a basal lamina and vasculogenesis are essential components, and embryonic molecular signals persist and play critical roles. The SVZ and SGZ can be viewed as "displaced" neuroepithelium, maintaining embryonic characteristics to support lifelong neurogenesis. Astrocytes in these regions, particularly those in the SVZ, exhibit neurogenic stem cell properties, challenging traditional views on brain development and stem cell identity. The neurogenic behavior of SVZ and SGZ progenitors is regulated by signals specific to their niches, and the SVZ and SGZ microenvironments direct neuronal differentiation. The SVZ and SGZ also contain a basal lamina that may be crucial for stem cell maintenance. Vasculogenesis and neurogenesis are closely linked, with vascular endothelial growth factor (VEGF) playing a significant role. Carbohydrate moieties like LeX and signaling molecules like Eph/ephrins also contribute to the niche environment. Developmental signaling pathways such as Notch, Shh, and BMPs are retained in adult germinal niches and regulate proliferation and differentiation. Intrinsic factors like Bmi-1 and TLX are important for adult neural stem cell maintenance. The adult neurogenic niche may be a "pocket" that retains embryonic signals, allowing some astrocytes to function as stem cells.The adult mammalian brain retains neural stem cells that generate new neurons in two restricted regions: the subventricular zone (SVZ) and the dentate gyrus subgranular zone (SGZ). These niches, which are spatially isolated and serve different brain systems, share common features: astrocytes function as both stem cells and niche cells, a basal lamina and vasculogenesis are essential components, and embryonic molecular signals persist and play critical roles. The SVZ and SGZ can be viewed as "displaced" neuroepithelium, maintaining embryonic characteristics to support lifelong neurogenesis. Astrocytes in these regions, particularly those in the SVZ, exhibit neurogenic stem cell properties, challenging traditional views on brain development and stem cell identity. The neurogenic behavior of SVZ and SGZ progenitors is regulated by signals specific to their niches, and the SVZ and SGZ microenvironments direct neuronal differentiation. The SVZ and SGZ also contain a basal lamina that may be crucial for stem cell maintenance. Vasculogenesis and neurogenesis are closely linked, with vascular endothelial growth factor (VEGF) playing a significant role. Carbohydrate moieties like LeX and signaling molecules like Eph/ephrins also contribute to the niche environment. Developmental signaling pathways such as Notch, Shh, and BMPs are retained in adult germinal niches and regulate proliferation and differentiation. Intrinsic factors like Bmi-1 and TLX are important for adult neural stem cell maintenance. The adult neurogenic niche may be a "pocket" that retains embryonic signals, allowing some astrocytes to function as stem cells.