A team of scientists led by Bruce Cohen of Lawrence Berkeley National Laboratory’s Molecular Foundry, a U.S. Department of Energy (DOE) nanoscience center, has figured out how to grow light-emitting nanocrystals small enough to not disrupt cell activity but bright enough to be imaged one at a time. This research aims to study protein behavior by tagging with light-emitting probes. The approach is to make upconvertingnanoparticle probes small enough to not disrupt protein behavior. The advantage of upconverting nanocrystals is that cells don’t upconvert light themselves, and the near-infrared light produced by the crystals is a lot less damaging to cells than visible or ultraviolet light.