Cover legend: Differentiated astrocytes, expressing glial fibrillary acidic protein (red), migrating outwards from a neurosphere after treatment of neural precursors with bone morphogenetic protein 4. Nuclei are stained blue. Transplantation of such cells is neuroprotective in a mouse model of tauopathy. Image copyright 2010 Daniel Webber. See the article by Hampton et al. in this issue (pages 9973–9983).