Carlos A. Meriles

A diamond speck smaller than a hundredth of a millimeter glows red. Inside it is a crystal defect: two neighboring carbon atoms, where one is missing and a nitrogen atom sits nearby. Such a pair captures light and re-emits it, like a tiny beacon that doesn't fade at room temperature. This speck was brought near a pathway on the chip's surface.

A tiny magnet made of layers of sulfur, chromium, and bromine sits on a microscope stage. Inside it, like unexpected guests, sit erbium atoms — a rare-earth metal. These atoms can glow when hit with a laser, and their light tells us what's happening around them.