In H. G. Wells’ The Invisible Man, the protagonist Griffin performs a mysterious procedure upon himself to become invisible. In Marvel’s Fantastic Four comics, it’s a dose of “cosmic rays” that gives the Invisible Woman her powers. And at Stanford University, it’s a technique called CLARITY that renders a mouse brain transparent.

Most of the time, we’re probably pretty glad that we can see mice. But when you want to study their brains, their opaque nature becomes a huge pain in the backside. Say you want to find out where a certain chemical is in the brain, like the amyloid-beta protein that underlies Alzheimer’s disease. It’s easy enough to make molecules that will stick to the protein and glow—that’s called immunolabelling.