Coupling molecular excitations to a cavity photonic excitation causes a hybridization of both types of excitations, leading to the creation of new light-matter hybrid states. When the PESs of the molecular ground and excited states are considered, the light-matter hybridization creates hybrid polariton surfaces, as discussed in Sec. 1.1 (see Eq. 11). These polariton surfaces hybridize the curvatures from both the ground and the excited molecular states (see Fig. , Fig. , and Fig. ) and possess different levels of matter or photonic excited character as a function of their nuclear coordinates (as we have seen). Additionally, the curvature of these surfaces is modulated by the Rabi splitting and creates new light-matter avoided crossings. These features of the potential energy surfaces can modify the path that a chemical reaction takes, resulting in a polariton-induced change of reactivity. By tuning the cavity frequency ω c and light-matter coupling strength g c , the features of these hybrid polariton surfaces can be optimized to control the outcomes of a variety of photochemical reactions.