This book provides a recipe for creating materials with a desired refraction coefficient, and solves the many-body wave scattering problem for many small impedance bodies. The physical assumptions make the multiple scattering effects essential. Technological problems are formulated which, when solved, make the theory practically applicable. The importance of a problem of producing a small particle with a desired boundary impedance is emphasized, and inverse scattering with non-over-determined scattering data is considered.