How do electrical impulses traveling among a tangle of neurons drive complex behaviors? Researchers seeking the answer have reconstructed the complete wiring diagram, or connectome, of the fruit fly’s adult brain—a feat akin to mapping all the buildings, avenues, and streets in a complex city. ⁠ ⁠ The comprehensive map will advance research on the neural activity that underlies fundamental processes such as walking and seeing in Drosophila melanogaster, an insect species widely used as a model o