Inspired by 3-D printing, researchers explored development of one mechanical property called effective static compressibility. As they now report, by using a single cartridge it’s possible to print a metamaterial which expands in size under hydrostatic pressure, even though it’s made up of material which behaves normally under hydrostatic pressure — that is, it shrinks. In principle, there is no limit to the negative value this material’s effective compressibility can take.