Microwaves are a fine way to warm water. So are stoves. But neither of them quite compare to dropping in a sphere of red-hot nickel to do the trick. Thanks to a little something called the Leidenfrost effect, the ball actually surrounds itself with a blanket of steam that keeps the rest of the water away.
Until the ball cools off just enough that it can't keep it up and then boom, crazy sounds and a puff of steam. It's the same thing that lets you dip your hand in molten lead, but backwards. And this little clip lets you really see how it works. Now somebody get me a blowtorch and some ball bearings because I need my coffee. [Reddit]