Piezochromism in non-molecular solids has been studied extensively, e.g., in perovskites, but the focus here lies on molecular compounds. In this realm, it has been noted that different crystal structures may yield different piezochromic responses. A tremendous amount of effort has been devoted to quantifying the effects of pressure-induced intramolecular structural changes and intermolecular interactions on piezochromism. At the singlemolecule level, the compression of a molecular scaffold should intuitively cause a blue shift of the UV/Vis absorption bands, as suggested by the particle-in-a-box model. In fact, XP-PCM in combination with symmetry-adapted cluster configuration interaction (SAC-CI) has shown that some absorption bands in the furan molecule are blue shifted under pressure. However, the authors of this study pointed out that, experimentally, a red shift is observed, which is likely due to intermolecular effects. Nevertheless, the value of computational methods like XP-PCM lies in the fact that they allow in-depth analyses of single-molecule effects in piezochromic materials.