Across the world, scientists are still trying to answer one of medicine’s most difficult questions: how can we safely and effectively treat brain cancers such as glioma? Despite decades of effort, outcomes for people diagnosed with high-grade glioma remain bleak. Current treatments, including surgery, radiotherapy, and chemotherapy, can slow the disease, but rarely stop it. The GlioLighT consortium, a multidisciplinary European research team funded by the European Innovation Council, has come together to explore a novel approach based on direct light therapy. Being in a very early stage, the project doesn’t promise an immediate cure; instead, it sets out to answer a very fundamental question: can light itself trigger biological processes that might form the basis of a safe and targeted brain tumor therapy?