Ultra-Ultra-Light Metal
The pic says it all:
It’s called an ultralight metallic microlattice, and it’s produced in an intriguing way. The method involves using a liquid photopolymer which solidifies when hit by ultraviolet radiation. Scientists shine light on the liquid through a pattern. Only the exposed bits of the liquid become solid, creating a lattice-work scaffold, which is then coated with nickel-phosphorous. Once the photopolymer is etched away, all that is left is a 3D, hollow lattice of metal which is more air than anything else.
This stuff weighs less than one milligram per cubic centimeter, completely bounces back after compression, and is made of a repeating lattice. It has incredible potential for use as thermal insulation; acoustic, vibration or shock dampening; energy absorption and recovery; and electronic parts.
The video is pretty cool:
http://io9.com/5860930/watch-ultra+light-metal-in-action