I'm tempted to say this is *magic* and take my show on the
road cooking food for kids' birthday parties. But I haven't
perfected balloon animals yet, so I'll tell you the real
deal on this one as long as you promise not to give away
the secret to the trick.

The special ingredient in a microwave oven is an electron
tube called a magnetron. The magnetron generates super-high
frequency radiation, which is scattered through the chamber
by a special fan called a "stirrer." Radiation penetrates
the food and makes its molecules vibrate rapidly against
each other. Doing the forbidden dance long enough causes
friction between the molecules, and friction causes heat.