Researchers at the National University of Singapore have introduced “supercritical coupling,” a groundbreaking concept that greatly improves photon upconversion efficiency. By leveraging the phenomena of “bound states in the continuum” (BICs), the team has surpassed traditional limitations, enabling light to be trapped indefinitely in open structures. This advancement, which showcases an eight-order of magnitude increase in upconversion luminescence, has profound implications for the control of light emission at the nanoscale, potentially impacting quantum photonics and other areas of photonic devices. Published in Nature, this work signals a paradigm shift in nanophotonics and opens new avenues for research.