Transformation optics is the field of study that maps curved spaces like
those in general relativity to anisotropic media that can be constructed
as metamaterials. The result is the near-total control of the path of light.
Many applications have been considered, but most famous is the cloak
of invisibility, which causes light to bypass a given region, rendering
anything in it invisible to the outside. This figure illustrates our
transformation-optics simulation of a 2D invisibility cloak, with red and
blue regions representing peaks and troughs, respectively, of the
steady-state electromagnetic wave, originally incident from below.
The white spot in the middle shows the cloaked region.