Examining a nanocrystal that shines on and off indefinitely

In 2021, lanthanide-doped nanoparticles made waves—or rather, an avalanche—when Changwan Lee, then a Ph.D. student in Jim Schuck's lab at Columbia Engineering, set off an extreme light-producing chain reaction from ultrasmall crystals developed at the Molecular Foundry at Berkeley Lab. Those same crystals are back again with a blink that can now be deliberately and indefinitely controlled.