Schematic (IMAGE) RIKEN Caption Near-infrared (NIR) light applied above the skull can easily pass through brain tissue with minimal scattering and reach deep structures. Up-conversion nanoparticles (UCNPs; blue) in the tissue can absorb this light and locally emit visible light sufficient to activate light-sensitive channels expressed in nearby neurons. Credit RIKEN Usage Restrictions credit RIKEN License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.