Clear Headed

Biologists usually have a 'bucket list' – details they want to know, hidden in delicate processes too fast or life-threatening to observe, or structures too small to see at all. Microscopy usually requires a compromise between the big picture and looking in detail. Here a new type of light sheet microscopy, called ExA-SPIM, allows scientists to see in high resolution over a wide area in a mouse’s brain. Zooming through the brain, we can see spindly neurons stretching out. The clarity of the image is thanks in part to techniques to first clear away opaque chemicals like fats, then to ‘expand’ the brain tissue – swelling it with salty liquid so its structures are easier to image. Fusing together multiple large image 'tiles' like this one allows the scientists to follow neurons running in all directions through the brain tissue, giving them a clearer picture of the connections inside.

Written by John Ankers

• Image from work by Adam Glaser and Jayaram Chandrashekar, and colleagues
• Allen Institute for Neural Dynamics, Seattle, WA, USA
• Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in eLife, June 2025