...The nascent invisibility cloak now being tested, for example, is made of a material that bends light rays "backward," a weird phenomenon thought to be impossible just a few years ago. Known as transformation optics, the phenomenon compels some wavelengths of light to flow around an object like water around a stone. As a result, things behind the object become visible while the object itself disappears from view.
"Cloaking is just the tip of the iceberg," said Vladimir Shalaev, a professor of electrical and computer engineering at Purdue University and an expert in the fledgling field. With transformation optics you can do many other tricks," perhaps including making things appear to be located where they are not and focusing massive amounts of energy on microscopic spots.
Other researchers are testing material that absorbs "99.955 percent of the light that hits it," making it by far the darkest material known. Very cool.