The last two decades of neuroscience were revolutionized by the fact that stem and progenitor cells exist in the adult brain throughout lifetime of mammals including humans. At least within the two classical neurogenic regions, the dentate gyrus in the hippocampus and the subventricular zone / olfactory bulb system, the stem and progenitor cells generate new neurons spontaneously and thus provide a continuous source for cellular homeostasis. In addition, it becomes more and more evident that progenitors outside of the typical neurogenic regions contribute to the generation of new cells in the brain. Hippocampal neurogenesis is tightly linked to memory function, the functional role of subventricular zone neurogenesis is less clear. The fact that neurogenesis can be modulated by molecular and cellular means, makes it an attractive target for neuro-regenerative approaches. This presentation will review the current knowledge on neural stem cells of the adult brain. It will touch basic science and clinical aspects of adult neurogenesis.