Positronium is formed when an electron pairs up with a positron, its antimatter twin.
First observed 2007. Lasts a few billionths of a second.
Now released in low temperature process from silicon, lasting 200 times longer than bound ones, 2011.
Related: 300 atoms of anti-hydrogen trapped for quarter hour at CERN, 2011.
Related: Anti-matter trapped in Van Allen belts.