One of the most interesting molecules is the Ribosome, the 'player' if you wish of an RNA molecule that assembles proteins out of the soup it floats in.
That just astounds and confounds me. An astonishing amount of stuff in just one cell! We're amazing beings at so many levels. Thank you for that link :)
https://en.wikipedia.org/wiki/Ribosome
It's a real life nano-assembler and there are billions of them in your body (and about 10 million give or take per cell).