A new optical imaging platform makes it possible to scan the activity of neurons across wider areas and deeper brain tissue, and even at different depths simultaneously. The platform is described in a paper published last month in Nature Methods. “This is a highly optimized system for two-photon voltage imaging,” says Adam Ezra Cohen, professor of chemical biology and physics at Harvard University, who was not involved in the work. Calcium indicators, which flash as calcium flows into neurons after they fire, have been the workhorse of optical brain imaging for over a decade. Genetically encoded voltage indicators (GEVIs) track neural activity directly, but, until recently, only over small areas, measuring up to about 50 × 250 μm and typically involving around 10 neurons.