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.
ATP synthase in action by HarvardX (2017)
Source.