A fridge magnet holds on thanks to many atoms aligned in one direction. But what if you take a single atom and ask it to remember which way it was magnetized? That's exactly what physicists did: they placed a dysprosium atom on a thin film of ordinary table salt and tested how long the atom holds its magnetic state.
The atom turned out to be stubborn. At a temperature of 2.5 K (just a bit warmer than absolute zero, where everything freezes), it kept its magnetization for about 10 seconds when sitting at a specific spot on the salt film. But if the atom landed on another spot, on top of a chlorine atom, it held on for a full 550 seconds. For comparison: in 550 seconds you can boil a kettle, and the atom 'remembered' its direction the whole time.
Such resilience opens the door to storing information at the scale of a single atom. Today, a hard drive writes a bit with thousands of atoms, but here it's one atom per bit. True, we're far from a home computer: you need a vacuum, cold, and a tunneling microscope. But the first step is done, an atom on salt has shown it can remember.
Dysprosium is a rare-earth metal that in pure form is as soft as lead and oxidizes quickly in air. Its name comes from the Greek 'dysprositos', meaning 'hard to get at'.
In Arthur C. Clarke's story 'The Nine Billion Names of God', monks use a computer to list all possible names of God — maybe someday atomic magnets will make such computations tiny and quiet.