The Ferrowatch from designer Karim Zaouai is the first watch to use Ferrofluids to tell time. A ferrofluid (or iron + fluid) is a liquid which becomes strongly magnetized in the presence of a magnetic field:

The watch’s face contains a small pool of the magnetic fluid and when held horizontally a magnetic backing creates animated gears and moving hands that indicate the time. And when the watch is tilted, instead of the fluid all spilling to one side, the last ‘image’ is frozen in place, once again thanks to the magnetic backing.

Don’t quite understand? Neither did we, but watch the video below to see it in action…

via OhGizmo