"Next time you stick a magnet to your fridge, you may be surprised to learn that you're using a quantum mechanical phenomenon.
Although magnetism has been known for centuries to be, quite literally, all around us (even our blood is magnetic!), scientists have just begun to understand in the past century that magnetism is a purely quantum mechanical phenomenon.
The Bohr-van Leeuwen theorem, which proved this, has been called one of the most deflationary theorems in modern science because it means that classical physics cannot account for magnetism, as previously thought."