The recent discovery of neural stem cells in the adult rodent forebrain advances attempts to develop treatments for neurodegenerative disorders and brain damage. However, to achieve this goal, the mechanisms that control adult neurogenesis must be understood. To investigate these, Laure Bally-Cuif and colleagues have turned to adult zebrafish, where they have now identified a pool of neural stem cells at the midbrain-hindbrain boundary (MHB; see p. 4293). They show that Her5 - one of the Hairy/Enhancer of Split [H/E(Spl)] transcription factors that regulates embryonic neuronal stem cells - is expressed in a few adult brain cells at the MHB. This cell population proliferates slowly, self renews, expresses neural stem cell markers and is multipotent in situ. The researchers propose that Her5 specifies both the adult and the embryonic neural stem cell state and suggest that a systematic examination of the expression of H/E(Spl) transcription factors in zebrafish adult brain might reveal new details about the regulation of adult neural stem cells.