The Haber process, also calle the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen and hydrogen, over an iron substrate, to produce ammonia. The Haber process is important because ammonia is difficult to produce on an industrial scale. Even though 78.1% of the air we breathe is nitrogen, the gas is relatively unreactive because nitrogen molecules are held together by strong triple bonds. It was not until the early 20th century that this method was developed to harness the atmospheric abundance of nitrogen to create ammonia, which can then be oxidized to make the nitrates and nitrites essential for the production of nitrate fertilizer and munitions.