(Half chatgpt half me) Meta materials or nano composites (they have a few names) are materials engineered to have properties not found in naturally occurring materials.
They are designed on a microscopic scale to manipulate electromagnetic waves in specific ways. This can result in unique optical, acoustic, and thermal properties, like being able to bend light or sound waves in unconventional directions. Common applications include advanced optics, wireless communication enhancements, and even invisibility cloaks and self cleaning surfaces in theoretical designs.
There is a really cool tinfoil hat (!!!) story on how we discovered they are possible, Lets say that since certain events in Boston and Roswell The US Air Force seems to have kickstarted and is often involved in this research. In the posted article the The US Air Force Office of Scientific Research was also stated to be funding this research. Take it with a cool grain of salt.