Cover legend: Expression of Neurogenin3 (yellow) in ventral spinal cord progenitors (indicated by Nkx2.2 staining, purple) precedes neuronal differentiation (indicated by βIII-tubulin staining, light blue). Neurogenin3 in the spinal cord restricts the development of the serotonergic system to the hindbrain. For more details, see the article by Carcagno et al. (pages 15223–15233).