Tiny carbon tubes can be used to hide three-dimensional objects from view, according to a team of researchers. The nanotubes are one-atom thick sheets of graphene wrapped into cylindrical tubes. Engineers from University of Michigan found they could be used to obscure objects so that they appeared to be nothing more than a flat black sheet. The team suggest "forests" of the material may one day be used to cloak spacecraft in deep space. The group says the technology works because the nanotubes' "index of refraction [is] very close to that of air". This means they slow down light to a similar degree. As a result there is very little scattering of light as it passes from the air into the layer of nanotubes.