diamond

At left, natural diamonds glow under ultraviolet light owing to their various nitrogen-vacancy (NV) centers. At right, a schematic depicting the diamond anvils in action, with NV centers in the bottom anvil. The NV sensors glow a brilliant shade of red when excited with laser light. By probing the brightness of this fluorescence, the researchers were able to see how the sensors responded to small changes in their environment. (Image Credit: Norman Yao/Berkeley Lab; Ella Marushchenko)