“…The macroscopic physical properties tailored in the design of metamaterial may be, for instance, optical, electromagnetic, thermal, mechanical and any combination (and coupling) of many of them. For instance, the particular shape, geometry, size, orientation and arrangement of the microstructural elements affect, in some particular metamaterials, the propagation of waves in a not-often-observed manner, e.g., not allowing the propagation in some band gaps (see, e.g., [28][29][30][31]) even if such a property is not present in the material constituting the microstructural elements (see also [32][33][34][35] for others unusual wave propagation phenomena).…”