  The concept of metamaterials emerged in years 2000 with the achievement of
artificial structures enabling non conventional propagation of electromagnetic
waves, such as negative phase velocity of negative refraction. The
electromagnetic response of metamaterials is generally based on the presence of
optically-resonant elements (or meta-atoms) of sub-wavelength size and well
designed morphology so as to provide the desired electric and magnetic optical
properties. Top-down technologies based on lithography techniques have been
intensively used to fabricate a variety of efficient electric and magnetic
resonators operating from microwave to visible light frequencies. However, the
technological limits of the top-down approach are reached in visible light
where a huge number of nanometre sized elements is required. We show here that
the bottom-up fabrication route based on the combination of nanochemistry and
of the self-assembly methods of colloidal physics provide an excellent
alternative for the large scale synthesis of complex meta-atoms, as well as for
the fabrication of 2D and 3D samples exhibiting meta-properties in visible
light.
