By soaking a silica sponge with antimatter, physicists have made the first matter-antimatter molecules. With further refinement, the technique might be used to briefly condense antimatter into fluid or solid states or even to create the first gamma-ray laser.
About 10 years ago, researchers created atoms of antihydrogen by combining antiprotons and positrons, the antimatter equivalents of protons and electrons. By itself, antihydrogen is as stable as hydrogen, though it's difficult to store in our matter world because of antimatter's propensity to vanish in a flash of gamma rays as soon as it comes into contact with matter.
For more than 50 years, however, physicists have been able to create nucleus-free "atoms" consisting of one electron and one positron. Attracted by their opposite charges, electrons and positrons will orbit each other, as the stars in a binary system do.
Unlike antihydrogen, however this unusual matter-antimatter hybrid, called positronium, is