With Nitrogen what's going on is that there's a tiny bacterium using some seriously advanced chemistry to attach Nitrogen gas (ubiquitous in our air) to Hydrogen (from water which is also ubiquitous) to make ammonia‡, which can then easily be used to make organic molecules. Plants which have a symbiotic relationship with these bacteria are readily available and can be grown to "fix" nitrogen into your soil.

‡ What's advanced here is not spending a ludicrous amount of energy, we can fix nitrogen, but we use a factory with high temperature and pressure to make the conversion work, the bacterium does it happily inside a peanut plant.