Kryptonite is real.

In April, geologists in Serbia dug up a white, powdery mineral that they weren't sure what to make of. They turned it over to Chris Stanley, a mineralologist at London's Natural History Museum, who discovered that it had the same chemistry — sodium lithium boron silicate hydroxide — as the fictional kryptonite, the green glowing rock that, aside from Lois Lane, is Superman's only weakness. Its chemical make-up was revealed in the 2006 film Superman Returns in which villain Lex Luthor writes the formula on a box of rocks he steals from a museum. The real-life substance will be called jadarite, after the area of Serbia in which it was discovered. It can't be called kryptonite, alas, because krypton, the gas, is already a real element.