Xenon has done it again—shown itself capable of forming interesting chemical compounds, that is. This time, those compounds take the form of perovskite crystals with the general formula, KMXeNaO6, where M refers to calcium or other group II elements (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201506690). The study shows that the noble gas, which was long thought incapable of forming molecules, actually forms quite an assortment of compounds. Sergey N. Britvin of Saint Petersburg State University and coworkers treated anhydrous sodium perxenate, Na4XeO6, with KOH solutions of the nitrates of calcium, barium, and strontium. The procedure yielded three-dimensional KMXeNaO6 perovskite framework compounds composed of alternating, corner-sharing XeO6 and NaO6 octahedrons. Xenon’s ability to work its way into perovskites may provide clues about the “missing xenon paradox.” Earth’s atmosphere contains far less xenon than expected based on analysis of ancient meteorites. Given that the main silicate in Earth’s interior is thought to be a MgSiO3 perovskite, and given that elevated temperatures and pressures induce xenon solubility in silicates, perhaps some of the missing xenon is hiding far below Earth’s surface, the team suggests.