Metamaterials can and have been designed and made to possess certain properties, even counter-intuitive ones.

ECONOMIST: Optical materials: Cast no shadows | The

"By using natural crystals for the first time, rather than artificial metamaterials, we have been able to scale up the size of the cloak and can hide larger objects, thousands of times bigger than the wavelength of the light, " said Shuang Zhang, the University of Birmingham physicist who led the research.

BBC: Invisibility cloaking benefits from crystal-clear idea