The periodic table may look like it has plenty of elements, but chemists and materials scientists would like more, thank you. That is because in the quest to design synthetic materials with unusually useful properties—say, a siliconlike superconductor with the biodegradability of wood—nature's cookbook has its limits. “Oftentimes you'll want an atom that actually doesn't exist,” says Colin Nuckolls, a professor of chemistry at Columbia University. Molecules built out of so-called superatoms—clusters of atoms that behave like single elemental units—could fill this need. Superatoms can be given electronic and magnetic properties that would be difficult or impossible to achieve using natural combinations of elements. But although chemists have known for decades how to create superatoms, a reliable way of linking them into larger structures has proved elusive.