With an increasing number of framework materials with predicted elastic constants published in the literature, it became clear that some properties considered as "rare" in crystalline materials actually have a higher prevalence than expected. For example, mechanical metamaterials 28 appear to be relatively common among MOFs, because of their dual organic-inorganic nature. In these meta-MOFs, the microscopic origin of the mechanical response is linked, for the most part, to the topology of the material: the framework acts like a macroscopic truss, where the organic linkers are the rigid struts, and metal centres act as hinges 29 -in a very similar fashion to how macroscopic metamaterials are designed, for example by additive manufacturing techniques. Based on large-scale databases like the one described above, it becomes possible to quantify how rare (or common) specific mechanical properties are among crystalline materials. In our group, Chibani et al. looked at 13,621 crystals from the Materials Project database and analyzed the anisotropy of their elastic properties: bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and linear compressibility. Among other conclusions drawn from this large amount of data, we could highlight the importance of elastic anisotropy and show that mechanics play a role in the experimental feasibility of inorganic compounds: materials with higher elastic anisotropy are mechanically more fragile. It was therefore possible to quantify, for the first time in a study of that scale, exactly how frequently those properties are encountered: negative linear compressibility is found in 3% of inorganic materials, while partial auxeticity (negative Poisson's ratio) is found in 30% -and therefore cannot be considered exceptional, as is often stated. Total auxeticity is the rarest of these phenomena, being observed in 0.3% of crystals studied, corresponding to a total of 30 crystals in the entire database.