In the quiet precision of a Korean laboratory, researchers at KAIST have found a way to read the invisible architecture of a battery electrode — measuring variations smaller than a ten-thousandth of a human hair — without ever breaking it open. The stakes are not abstract: uneven electrodes concentrate heat, and concentrated heat, in millions of electric vehicles, becomes fire. By marrying terahertz waves with optical frequency combs, two tools never before paired, the team has offered manufacturers a way to see what was previously unseeable, in real time, on the factory floor. It is a reminde