Cover legend: A 5-mm-long hatchling Xenopus tadpole is shown against a fragment of a minimal swimming network of 1,300 neurons and 85,000 synapses constructed by an axon growth model. Color-coded, mainly longitudinal axons from 7 types of neurons make synapses (circles) probabilistically with dendrites (vertical bars). For more information, see the article by Roberts et al. (pages 608–621).