Functional materials are generally characterized as those materials which possess particular native properties and functions of their own. For example, Ferroelectricity, piezoelectricity, magnetism or energy storage functions. Functional materials are found in all classes of materials: ceramics, metals, polymers and organic molecules. Functional materials are often used in electromagnetic applications from KHz to THz and at optical frequencies where the plasmatic properties of metals assume particular importance. Functional materials are also of critical importance in materials for energy such as electro- and magnetocaloric materials, for energy storage and for solar harvesting functions.