The adult mammalian brain retains neural stem cells in two regions: the subventricular zone (SVZ) and the dentate gyrus subgranular zone (SGZ). These niches, though spatially isolated, share common features, including astrocytes as both stem cells and niche cells, a basal lamina, and embryonic molecular signals that regulate neurogenesis. These niches function as "displaced" neuroepithelium, preserving embryonic characteristics to sustain neurogenesis throughout life. Neural stem cells and their niches are maintained in restricted regions of the adult brain, with local developmental processes occurring for the lifespan of the animal. Classic developmental signals like Notch, BMPs, Eph/ephrins, Noggin, and Shh play critical roles in maintaining these niches. In the SVZ, neurogenic stem cells are concentrated and migrate to the olfactory bulb, differentiating into interneurons. In the SGZ, neurons are born locally and integrate into the dentate gyrus. Astrocytes in these regions function as neurogenic stem cells, challenging traditional views of brain development and stem cell identity. The neurogenic behavior of SVZ and SGZ progenitors is determined by signals within their niches. Transplanted SVZ cells generate neurons in the olfactory bulb but not in nonneurogenic regions, indicating the importance of the niche. Cultured SGZ progenitors produce interneurons when grafted to the SGZ but not to nonneurogenic targets. The SVZ and SGZ microenvironments not only maintain stem cells but also direct neuronal differentiation. Astrocytes in the SVZ and SGZ are in close contact with other cell types and contribute to the creation of the microenvironment that stimulates neurogenesis. The basal lamina, rich in laminin and collagen-1, is essential for maintaining stem cell properties. The relationship between vasculogenesis and neurogenesis is significant, with blood vessels and the basal lamina playing key roles in supporting stem cells and their niches. Molecules like LeX, Eph/ephrins, and Notch signaling are involved in regulating the neurogenic niche. Shh and BMPs are also important, with Shh promoting neurogenesis and BMPs influencing astrocyte differentiation. These signaling pathways, along with intrinsic factors like Bmi-1 and TLX, are crucial for maintaining adult neural stem cells. The niche provides the necessary signals for stem cell self-renewal and differentiation, ensuring the continued generation of new neurons throughout life.The adult mammalian brain retains neural stem cells in two regions: the subventricular zone (SVZ) and the dentate gyrus subgranular zone (SGZ). These niches, though spatially isolated, share common features, including astrocytes as both stem cells and niche cells, a basal lamina, and embryonic molecular signals that regulate neurogenesis. These niches function as "displaced" neuroepithelium, preserving embryonic characteristics to sustain neurogenesis throughout life. Neural stem cells and their niches are maintained in restricted regions of the adult brain, with local developmental processes occurring for the lifespan of the animal. Classic developmental signals like Notch, BMPs, Eph/ephrins, Noggin, and Shh play critical roles in maintaining these niches. In the SVZ, neurogenic stem cells are concentrated and migrate to the olfactory bulb, differentiating into interneurons. In the SGZ, neurons are born locally and integrate into the dentate gyrus. Astrocytes in these regions function as neurogenic stem cells, challenging traditional views of brain development and stem cell identity. The neurogenic behavior of SVZ and SGZ progenitors is determined by signals within their niches. Transplanted SVZ cells generate neurons in the olfactory bulb but not in nonneurogenic regions, indicating the importance of the niche. Cultured SGZ progenitors produce interneurons when grafted to the SGZ but not to nonneurogenic targets. The SVZ and SGZ microenvironments not only maintain stem cells but also direct neuronal differentiation. Astrocytes in the SVZ and SGZ are in close contact with other cell types and contribute to the creation of the microenvironment that stimulates neurogenesis. The basal lamina, rich in laminin and collagen-1, is essential for maintaining stem cell properties. The relationship between vasculogenesis and neurogenesis is significant, with blood vessels and the basal lamina playing key roles in supporting stem cells and their niches. Molecules like LeX, Eph/ephrins, and Notch signaling are involved in regulating the neurogenic niche. Shh and BMPs are also important, with Shh promoting neurogenesis and BMPs influencing astrocyte differentiation. These signaling pathways, along with intrinsic factors like Bmi-1 and TLX, are crucial for maintaining adult neural stem cells. The niche provides the necessary signals for stem cell self-renewal and differentiation, ensuring the continued generation of new neurons throughout life.