If you want to shoo away a fly without waving your hands, try a laser. Just be sure to bathe its nerves in a light-activated chemical before zapping away at it, as Susana Lima and Gero Misesenböeck of Yale University have done. They engineered specific fly neurons to produce a rat protein that transmits an electrical signal when activated by the molecule ATP. Next they designed a chemical “cage” for ATP that dissolves when hit with ultraviolet laser light. Finally, they took advantage of a fly's emergency “fly away!” reflex, triggered by the insect's central nerve even when its head is gone. The two could send most zapped flies jumping and flying, even when the flies were blinded or beheaded. They also made slow-moving flies buzz around more excitedly by targeting different neurons. The technique, the investigators say in the April 8 Cell, may permit more precise studies of behavior and brain circuitry than electrodes do.