New archaeological research by Tulane University and the Proyecto Templo Mayor in Mexico reveals how obsidian—a volcanic glass used for tools and ceremonial objects and one of the most important raw materials in pre-Columbian times—moved across ancient Mesoamerica and shaped life in its capital, Tenochtitlan. The study sheds new light on the economic networks, rituals and political influence of the Mexica (Aztec) Empire.