Organonitrogen compounds are of vital importance to our lives.   For almost all organonitrogen compounds, ammonia is only the feedstock as a nitrogen source.   Ammonia is produced from dinitrogen (N2) and dihydrogen (H2) by the Haber-Bosch process, which consumes an enormous amount of energy.   As an alternative method to convert N2 into organonitrogen compounds under milder conditions, various stoichiometric reactions with transition metal complexes have been explored for the last 50 years.   However, the field of catalytic formation of organonitrogen compounds directly from N2 with transition metal complexes is still in its infancy.   This short review summarizes strategies to achieve the direct synthesis of organonitrogen compounds from N2 under mild reaction conditions using transition metal complexes ranging from stoichiometric reactions to catalytic reactions.