You may have heard of the Bose-Einstein Condensate because it is one of the states of matter. Like gas, liquid, or solid, it has its own properties. Predicted by a maverick physicist back in the early twentieth century, it was only proven to exist in 1995. And it's pretty damn weird.
Positronium is a particle created when you bind together an electron and its antimatter counterpart, the positron. It doesn't interact with other atoms in the way we would expect, and this discovery could help us solve the universe's biggest mysteries.