ELI5 Nitrogen - why does nobody talk about 78% of our air?

We talk so much about oxygen and carbon, but 80% of the atmosphere is nitrogen. How does it fit in? Why does it not get talked about? Why does 1% of the world’s energy go into speeding up the nitrogen cycle? Why do divers know a lot about nitrogen? Why is liquid nitrogen so useful? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: chicagofaucet, edman007-work, topomouse and scarabic. To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]