Coaxing light and matter to interact strongly enough to fully mix into coupled states has been the focus for scientists bridging photonics, materials and chemistry over the past three decades. Admixing states creates new quasiparticles with unusual material properties. Their pursuit is relevant to efficient low-threshold lasers, nonlinear optical materials for switching that outperform anything previously available, and solid-state Bose–Einstein condensates that underpin quantum technologies. Writing in Nature Materials, Jana Zaumseil and colleagues1 have developed a way to incorporate size-selected carbon nanotubes into micrometre-sized photonic cavities, fully mixing the excitons with light at room temperature and, crucially, demonstrating their simple electrical excitation.