Johannes (Jan) Zaanen, a leader in theoretical physics, died on 18 January. He was 66. His groundbreaking work, which explored the interplay between locality and long-distance physics, moved forward a broad range of fields, including the study of metal oxides, high-temperature superconductivity, and applications of string theory to condensed matter. Jan’s spitfire speech pattern took a while to decipher (similar to the ancient Greek Oracle of Delphi), but his work was well regarded as brillian...