A molecular state can be hybridized with a photon in a confined space, resulting in the formation of hybrid light-matter states (Figure 1).[1] These hybrid states behave like half-photon and half-molecule. The most interesting aspect here is that the states are formed by vacuum excitations, and therefore, external stimuli are not required. That means photochemistry without external photons![2] During the talk, I’ll introduce the concept of cavity QED and show a few experiments that we did at IISER Mohali, which include cavity catalysis[3] and other modifications of physical properties.[4] Currently, we’re working on polariton formation from atomic monolayers in both open and closed cavity configurations. The photophysics of such systems are clean and are achievable at room temperature. Vacuum engineering of the medium helps us to study in detail the momentum locking and inversion of group velocities.[5] We also discuss some of the applications of these systems that include the observation of exceptional points,[6] faster and long-range energy and electron transport through the hybrid states.[7, 8]