Structuring matter at the length scale of the wavelength allows modifying and controlling the propagation of waves. Periodic structuration, as an example, introduces domains of frequency where light cannot propagate even though the surrounding material is transparent like in opals. By combining the effect of long range ordering with the resonance effects in individual objects it is possible to generate new effects that are not accessible in natural materials : this is the domain of metamaterials which are developed at the INSP in the acoustics and in the optics domains. Beside bottom-up approaches, top-down approaches using liquid crystals for instance are investigated. A great source of inspiration comes from living organisms which have evolved to yield original and robust effects.
