Adenosine triphosphate (ATP)

The fact that ATP is the universal energy storage mollecule of all life on Earth is such an incredible unifying principle of biology!

It is the direct output of all the major forms of "energy generation" in cells: ATP synthesis mechanism.

It is just as fundamental as the genetic code for example.

No wonder dozens of Nobel Prizes were related to its discovery, given its complexity.

ATP is the direct output of all the major forms of "energy generation" in cells:

One of the most beautiful molecular machines known!

The first one with such complexity that was uncovered.

The thing rotates like a water wheel for God's sake, except it uses protons instead of water.

The ATP synthase complex is so large that Power, Sex, Suicide by Nick Lane (2006) page 123 contains a cryoEM image of several ATP synthases on small membrane vesicles, this is the paper: pubs.acs.org/doi/abs/10.1021/bi00437a031# under a fucking paywall.