Wiring the developing insect brain Developmental brain wiring requires a complex set of cellular interactions often orchestrated by a large number of surface receptors. Thousands of Dscam1 receptor isoforms function as “surface tags” endowing neurons with unique molecular identities. These isoforms are important for neuronal self-recognition and dendrite self-avoidance. He et al. report that the diversity of Dscam1 isoforms is also essential for complex axonal branching of sensory neurons in developing fruit flies. Science , this issue p. 1182