In 1893, Alfred Werner authored a paper of major chemical signi‘cance. Breaking with traditional chemical thinking, he proposed an entirely new molecular structure to describe atoms that could exist in more than one valence state and form highly stable compounds. Werner noted that certain structural entities, which he called “complexes,” would remain intact through a series of chemical transformations; he wrote, “If we think of the metal ion as the center of the whole system, then we can most simply place the molecules bound to it at the corners of an octahedron.”1 He used platinum bis-ethylenediamine chloride to illustrate his theoretical concept.