Nothing can do something: Manipulating materials by tailoring the electromagnetic vacuum

Light–matter interactions are at the core of many physical and chemical processes, but when these interactions are confined to the nanoscale, entirely new phenomena can emerge. In this talk, I will present our recent explorations of how strong coupling between photons and excitons gives rise to hybrid light–matter states with novel optical and electronic properties. I will discuss how such effects can modify energy flow, emission, and even chemical reactivity, pointing toward new horizons in material sciences.