On the surface of a thin film of bismuth iron oxide, you can see neat stripes, like furrows in a plowed field. What lies beneath them has remained a mystery until now. A new device called DREDI shines electrons through the material and, in a fraction of a second, builds a map of electric fields at different depths with precision down to ten nanometers: that's a thousand times thinner than a human hair.

Below the surface, the stripes don't vanish; they twist into vortices, like whirlpools in a river. Deeper still, near the bottom, each vortex splits into three arms, like a river branching into channels. These triple junctions arise because the bottom layer of the material is slightly compressed and cracked, and those cracks force the electric fields to change direction.

Such tangled electric patterns could become the basis for future memory: instead of storing bits as charge, you could use the direction of the vortex's twist. And the new DREDI method lets us observe these patterns in 3D and in real time for the first time, like watching the flow of a river without diving in.