Any theoretical attempt to explain the rate modulations under VSC condition has to explicitly deal with the phenomenon of vibrational resonance since, experimentally, the key idea involves tuning the cavity frequency ω c to specific mode frequencies of the reactant molecule. In this context we mention that experimentally the cavity-mode resonance is observed only for normal incidence i.e., when the in-plane photon momentum k ∥ is zero. Although this has been rationalized based on the argument that at k ∥ = 0 one has ideal lightmatter hybridization, a convincing theoretical explanation is still absent. In addition, note that in multimode molecules it is not necessary that ω c has to be resonant with the frequency of the bond that is directly involved in the reaction . Due to anharmonicity, cavity coupling to an auxiliary mode can lead via IVR to population transfer to the reactive mode. Given that frequency commensurability leads to energy transfer between the modes involved, IVR has to be one of the principal agents which drives the cavity-mediated chemistry. In the quantum domain such commensurabilities are referred to as Fermi (anharmonic) resonances and in the classical limit the Fermi resonances are related to the existence of specific nonlinear resonances in the phase space. In fact, the network of classical nonlinear resonances also provides a scaffolding for purely quantum routes to energy flow . Schäfer et al in their detailed dynamical study of the molecule relevant to the original experimental study provided the first evidence that cavity-mediated IVR pathways led to the suppression of dissociation rate. At the same time their study illustrated the complexity of the energy flow dynamics in the cavity-molecule system -perhaps not entirely un-expected, given the fact that the mechanism of IVR is far from simple even in the absence of coupling to the cavity. Further example for the nontrivial role of IVR was provided by Sun and Vendrell in their work on the isomerization of the HONO molecule. More recently, Gomez and Vendrell presented a model where anharmonic intramolecular resonances can lead to facile energy exchange between the upper polariton and the dark states. A key observation is that this mechanism of populating dark states is robust in the collective VSC regime. A recent combined theoretical and experimental work of Ahn et al on resonant suppression of the rate of alcoholysis of phenylisocyanate highlights the role of Fermi resonances in cavity-mediated chemistry.