The Relativistic Heavy Ion Collider (RHIC) is the first machine in the world capable of colliding heavy ions, which are atoms which have had their outer cloud of electrons removed. RHIC is the first and one of only two operating heavy-ion colliders, and the only spin-polarized proton collider ever built. It primarily uses ions of gold, one of the heaviest common elements, because its nucleus is densely packed with particles. Physicists from around the world are using the Relativistic Heavy Ion Collider to explore some of Nature’s most basic — and intriguing — ingredients and phenomena. Visit the website.