Metamaterials are artificial electromagnetic materials, that can be designed to have properties that are difficult or impossible to achieve with conventional, naturally occurring materials. Built from microstructure that is small compared to the wavelength of operation, metamaterials can be designed with effective permittivity and permeability values that can be large or small or even negative at any selected frequency. The engineered response of these artificially constructed metamaterials has had a dramatic impact on the physics, optics, and engineering communities, as we can now make practical materials exhibiting physical phenomena such as a negative refractive index, that were previously only theoretical exercises. In this paper, I will review the development of metamaterials, and discuss their use to control electromagnetic fields and hence to make lenses with sub-wavelength resolution and a cloak of invisibility.
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