Two high-speed electron microscopes. 7,062 brain slices. 21 million images.For a team of scientists at the Howard Hughes Medical Institute's Janelia Research Campus in Ashburn, Virginia, these numbers add up to a technical first: a high-resolution digital snapshot of the adult fruit fly brain.Researchers can now trace the path of any one neuron to any other neuron throughout the whole brain, says neuroscientist Davi Bock, a group leader at Janelia who reported the work along with his colleagues on July 19, 2018, in the journal Cell."The entire fly brain has never been imaged before at this resolution that lets you see connections between neurons," he says. That detail is key for mapping out the brain's circuitry—the precise webs of neuronal connections that underpin specific fly behaviors.