Neurodevelopment Stem cells in the developing brain acquire identities according to their locations and the types of neurons they will generate. As the brain grows larger and more complex, these identities must be maintained. Delgado et al. found this positional identity to be sustained by an epigenetic memory system. A morphogen sets the stem cell's identity early in development, but the identity is sustained by epigenetics. Science , this issue p. [48][1] [1]: /lookup/doi/10.1126/science.aba5960