In Ref. 69, it was theoretically demonstrated that the cavity photon mode acts as a non-Markovian solventlike degree of freedom that is coupled to the molecular reaction coordinate R, such that the presence of photonic coordinate enhances the recrossing of the reaction coordinate and decreases chemical rate. In simple chemical processes and enzymatic catalysis, a closelyrelated phenomenon is referred to as the "dynamical caging" effect, 389-393 which has been well explained by the Grote-Hynes (GH) rate theory. Due to the low frequency of the cavity mode (in comparison to polariton photochemistry), which is in the same frequency range as the vibrational frequencies, both R and q c are treated as classical DOFs in Ref. 69, and the GH theory is used to study how the cavity mode affects the dynamics of a reaction. In Ref. 69, such a classical description was employed to investigate cavity-modified ground state chemical rate for a single molecule coupled to a single cavity mode. The model system is described by ĤPF (Eq. 192), where the choice of E g (R) is the ground state potential of the Shin-Metiu hydrogen atom transfer model. The key results of these studies are summarized in Fig. . Fig. presents the absorption spectra of the polariton system, where with an increased light-matter coupling strength η (Eq. 194), the Rabi splitting Ω R also increases accordingly as observed in the absorption spectra. Fig. presents the transmission coefficient, κ, computed numerically using Eq. 200 (dots) or obtained using the GH theory through Eq. 201 (solid lines). Since k TST remains invariant inside and outside the optical cavity, κ directly reports the absolute change of the overall rate constant (see Eq. 199). In this panel, we present the change of κ when the molecule is coupled inside the cavity, with a range of cavity photon frequency ω c . Three different light-matter coupling strengths, η = Ω R /2ℏω c , were chosen corresponding to the Rabi-Splitting observed in the absorption spectra shown in Fig. . The cavity modified transmission coefficient κ in Fig. clearly shows the cavity frequencydependent suppression of chemical rate, which was not observed when only considering the TST level of theory 371 or when ignoring DSE. 381 At a fixed light-matter coupling strength A 0 , the transmission coefficient κ is minimized at a frequency ω min c that is related to the imaginary barrier frequency ω ‡ . This effect can be phys-ically understood as the cavity dynamically caging the reaction coordinate R near the barrier leading to a reduction in chemical rate. Further, one can also understand the significant red-shift of the ω min c , with the detailed theoretical explanation provided in Ref. 69. We emphasize that there are no existing experiments that report that matching cavity frequency ω c with the top of the barrier frequency ω ‡ will suppress the rate constant, under the single molecule limit. So even though there is a similarity between theory (Fig. ) and experiment (Fig. ), one must clearly understand that they are under very different coupling limits (single molecule for theory, and collective coupling for experiments) as well as at what photon frequency cavity most strongly modifies chemical reactivity. For the classical theories discussed above, it is when ω c ≈ ω ‡ , and for experiments, it is ω c ≈ ω 0 (reactant well frequency). Nevertheless, the dynamical caging effect has also been observed in the ab-initio VSC dynamics simulations 380 of the reaction in Fig. . With the plasmonic cavity setup or the epsilon-near-zero cavity, 34 it is possible to confine IR frequencies and even achieve an ultra-strong coupling regime for just a few (or a single) molecules. Thus, besides the purely theoretical value, the prediction in Fig. might also be within the reach of near-future experimental setups.