There is a not-very-documented feature in MacOS 10.9 that I just stumbled upon.
If you save a text file in SMILES format, Mac will show the correct image, scalable, in preview.
This is a very simple text file. It’s the shorthand for the chemical structure of DDT, and its sole content is
which is the Simplified Molecular-Input Line Entry System, or SMILES, abbreviation.
It doesn’t make that the icon of the file, just next to it you can see the BBEdit document for a really large molecule (which also renders) that I copied from the Wikipedia entry on SMILES.
Now, I’m nowhere near geek enough to dig into the UNIX guts and find the function call. But it’s pretty cool.