The researchers made the molecules by slowing antiprotons and letting them interact with hydrogen molecules, leading to molecules consisting of a single proton bound to a single antiproton, as well as leftover hydrogen atoms.
(Bear in mind that scientists have long ago managed to join electrons and positrons together into positronium, which is a lot like a molecule, but molecules really should have atoms in them, rather than just electrons and their antimatter positron partners.)
Now the big question — what do we call the stuff?
The CERN folks are going with “antiprotonic hydrogen.” A bit hard on the tongue, I think.
My friends at Physics News Update (PNU), who reported the story first, like “protonium.” That’s probably the best bet, but if we are following convention established with positronium (which is named after the antimatter particle), it should be called “antiprotonium.”
Wikipedia already has an entry for protonium, so I think my PNU friends have made the right call.
Regarding the graphic above, you can’t really take pictures of atoms and small molecules, but these shapes (spherical harmonics) are closer to the way hydrogen atoms would actually look if you could see them. If CERN releases images of protonium/antiprotonium/anitprotonic hydrogen, I’ll post those instead.