Ammonia production is a very energy- and capital-intensive industry as it requires high temperature (400-500°C) and also high pressure (150-300 bar) for its daily operations. Two moles of ammonia are obtained by reacting one mole of nitrogen and three moles of hydrogen gases in the presence of conventional catalyst which is magnetite. The process to produce ammonia is known as Haber-Bosch process which was developed and patented by Fritz Haber and Carl Bosch in 1916. Since then more work on ammonia production was carried out with the aim to obtain higher ammonia yield. Catalytic reaction giving emphasis on types of catalysts was reviewed in this chapter. Different catalysts synthesis methods and their characterisations were also reviewed A variety of microreactors were proposed by different authors and some patent fillings have been described. A new method to synthesize ammonia at room temperature and ambient pressure were described. The reaction was done in 1 T magnetic field. This work offers the ammonia producers a potential contender in the market place. © Springer-Verlag Berlin Heidelberg 2010.