Everyone knows that many organic solvents won’t mix with water (or, more generally, some polar solvents won’t mix with some nonpolar solvents). What you might not know is that some highly fluorinated liquids aren’t very polar at all, but they won’t dissolve in water or many organics.
In fact, you can mix certain organic solvents, the fluorous stuff, and water, and end up with three phases! The company in that link has made a business of using perfluorinated tags to stick on your molecule, which in turn stick to a perfluorinated solid support (you later wash off your stuff with something that gets along with the fluorous tag).
3M sells a mixture of fluorinated light hydrocarbons known as “fluorinert” that include molecules such as the above. The bizzareness of fluorine defines these compounds – not only are their solubility characteristics unique, they are really stable thanks to a strong carbon-fluorine bond, making them one of those rare small alkyl halides that aren’t toxic – it’s even possible to breathe them!