The scientists were able to cloak a centimeter-scale cylinder and make it completely invisible to microwaves. The problem with creating invisibility cloaks is that the structures required for the technology are difficult to make. Previously, scientists had been unsuccessful in making their object completely invisible to the wavelength they were working in.
Two researchers from Duke University named David Smith, and Nathan Landy have conducted research that involved reworking how the edges of their microwave cloak lineup to ensure that light passes around the cloak completely with no reflections. The scientists used a diamond-shaped cloak that involved carefully matching the diamond corners to perfectly reflect light around a cylinder that measured 7.5 cm in diameter and 1 cm tall.
The result of the test was perfect invisibility according to Professor Smith. While the cylinder was completely invisible, the illusion only works in one direction. The scientists say this is akin to being able to see a playing card when looking at its flat surface, but not being able to see it when itís looked at from the side. The scientists also point out that principles used in making their microwave cloak work would be difficult to implement for optical wavelengths of light. However, making the object invisible to microwaves is of use in applications for telecommunications and radar.
source: Scientists successfully cloaked an object perfectly for the first time - SlashGear