The brief historical description offered in Chapter 1 showed how the initial studies of materials with both ε < 0 and μ < 0 (Veselago 1968) did not spark much interest at first because such materials were not available at the time. Their realization had to wait for more than three decades before the recipes for achieving ε < 0 and μ < 0 (Pendry et al. 1996; 1999) paved the way for experimentalists to design these materials. It was the first experimental demonstrations of such media (Smith et al. 2000, Shelby et al. 2001b) at microwave frequencies that caused most of the scientific community to sit up and take notice. The subsequent fevered advances in this area are now history, but one has to remember that it was the new design principles within a physical paradigm that made this whole area relevant.