As recently as this summer, invisibility cloaks were only a theoretical possibility. Now the world's first cloaking demonstration has bent microwaves around a 7.2-cubic-inch enclosure, effectively hiding it from detection. The proof of concept suggests how engineers might pattern split-ring resonators to create "designer" metamaterials. Split-ring resonators--free-space rings of metal with a gap that prevents them from being a complete ring--are usually patterned on a fiberglass circuit board. When microwave radiation passes through them, they act as a dielectric whose magnetic permeability and electrical permittivity can be custom-tailored by adjusting the size and shape of the resonator. The cloak demonstrated earlier this month was designed to bend microwaves. But the researchers claim that with more engineering effort, EEs could create invisibility cloaks for any type of electromagnetic radiation, even visible light.