Existing histories claim theory drove chemistry's remarkable nineteenth-century development. This talk shows instead how chemists used novel experimental approaches and what Jackson calls “laboratory reasoning” to create the molecular world. Built on practice-based breakthroughs – including the “glassware revolution,” the turn to synthesis, and the “chemical identity crisis” – this historical reassessment reveals organic synthesis as the ground chemists stood upon to forge a new relationship between experiment and theory—with far-reaching consequences for chemistry as a discipline