In 1909, Fritz Haber demonstrated that atmospheric nitrogen could be fixed into ammonia using an iron catalyst under high pressure. Carl Bosch then scaled the process to industrial production at BASF in Karlsruhe, Germany. The Haber-Bosch process broke the biological monopoly on nitrogen fixation, enabling mass production of synthetic fertilizer. Estimates suggest roughly half of the nitrogen in human bodies today derives from this process. The same chemistry also enabled production of explosives, linking the invention to both agricultural expansion and modern warfare.