Owing to its incredible stability, the reduction of dinitrogen (N2) to ammonia (NH3) requires a substantial energy input. Industrially, the Haber–Bosch process is used for this conversion, using 2% of world energy production to generate ammonia for use in fertilizer. As such, there is much interest in engineering crops equipped with effective nitrogenase enzymes, able to convert atmospheric nitrogen to bioavailable ammonium. Now, writing in Nature Catalysis, Oliver Einsle and co-workers from the University of Freiburg have uncovered the structure of the Fe-only nitrogenase, and used this to better understand the mechanism of nitrogen fixation across all nitrogenase isoforms.