The key is an innovation that’s being called ‘light beads microscopy’. It improves on current two-photon microscopy, using lasers to trigger introduced fluorescence in living cells. As the cells are lit up, scientists can see how they’re moving and interacting.

With light beads microscopy, scientists can get the speed, scale, and resolution required to map a mouse brain in detail as its neural activity changes. The near-simultaneous tracking can last for as long as the light beads are able to stay illuminated.