Fig. presents several recent works on modifying the ground state properties when coupling molecules to a high frequency cavity (in the electronic excitation range). Fig. examines the effects of modulating inter-molecular interactions by coupling an H 2 dimer to a cavity with frequency ω c = 12.7 eV and coupling strength λ = 0.10 a.u. 101 Using the coupled cluster (CC) and full configuration interaction (FCI) methods, as well as their scQED variants, QED-CC and QED-FCI, 100,101 it was determined that the presence of the cavity drastically modulates the inter-molecular interactions between the two H 2 molecules. Depending on the cavity polarization direction with respect to the hydrogen dimers, the inter-molecular potential well can be increased by ∼ 0.75 meV (for êz polarization along the inter-molecular axis) or decreased by ∼ 1.0 meV (for êx polarization along the intra-molecular bond axis), respectively. These weak inter-molecular interactions, on the order of meV, are ubiquitous in chemistry. As such, a drastic change in the intermolecular potential may give new and interesting effects in many of these processes. In this simple example, the well was modified by up to 100 % compared to outside of the cavity.