Principal gas-phase reactions involved in the first stages of nitrogen interstellar chemistry in dark clouds. Nitrogen hydrides (blue, left) and nitriles (red, right) have been clearly separated. The main formation route of NH is highlighted (green). Chemical pathways from nitrogen hydrides to nitriles, which are efficient at specific C/O ratio ranges, are also represented (dashed yellow). Adapted from Hily-Blant et al. (2013a).