Some more information about optical invisibility, distinct from the electromagnetic invisibility I talked above: the invisibility is that phenomenon where light rays deflect when they income over the object, and then they rejoin at the back of the same object. Invisibility in the visible light range has been obtained by two distinct research groups under suitable conditions, with polarized light and in a high-refractive medium. In 1964 Russian physicist Victor Veselago proposed his theory on negative refractive index where light is deviated in “wrong way” and in 2000 this metamaterial was realized by Professor Sir John Pendry and colleagues from Imperial College and the University of California at San Diego. It has been demonstrated that negative refractive index metamaterials can be used to conceal objects. However until now invisibility has been obtained only for small objects under very constrained conditions.