In the course of global change throughout the Archean, Proterozoic and Phanerozoic, the N concentration in the atmosphere increased sharply at the out-going Archean and beginning of the Proterozoic age, decreasing thereafter mainly during the Phanerozoic analog to the increase of O2 due to enhanced aquatic and terrestrial actions of photosynthesis. At present, atmospheric N comprises about 3.8 Mil Gt, in the lithosphere ca. 19 Mil Gt and in terrestrial organic matter about 95 Gt N. In modern anthropogenic global change, the NOx compounds, especially the very stable N2O with 170 yrs residence time and a molar greenhouse forcing efficiency factor of 150 compared with CO2, is highly relevant for greenhouse forcing as well as for reduction of the UV b absorbing stratospheric ozone layer. The 0.3 ppm N2O, representing ca. 1.5 Mt N, is increasing by ca. 0.3% y-1 — about 1 ppb·y-1. Some 85 to 90% are of biotic origin, equal to ca. 7 Mt N2O y-1, emitted from soil and soil near atmosphere and about 3 Mt N2O y-1 in connection with N-fertilizer. It has become obvious that N2O emission is highest from wetlands and especially from moist tropical woodlands and patches of forest clearing. Sources are denitrification and nitrification especially of heterotrophic origin. NH3 vemission amounts to 22–35 Mt N·y-1 with ruminant husbandry as the main contributor. In soil organic matter the average C:N:P:S ratio is about 140:10:1:3:1.3 with most likely a wider C:N in soils of tropical rainforests. C and N emissions due to shifting cultivation, wood clearing, savanna fires, agricultural wastes are estimated to 1.8–4.7 Gt C and 0.015–0.046 Gt N y-1 with a C:N of ca. 100:1. NO, with only a few days residence time in the atmosphere, originates in the stratosphere as an ozone killer from N2O oxidation. In the atmosphere, if available at concentrations > 10 ppT, it contributes to the production of ozone as a by-product of CH4 and CO oxidation; if NO is < 10 ppT, it consumes slight amounts of tropospheric ozone during CH4 and CO oxidation. NO in cell physiology is an outstanding intracellular messenger compound, produced from the amino acid arginine.