Science & TechHow it works
Why the microwave heats your soup but not the plate.
A microwave oven emits radio waves at 2.45 GHz. Water molecules are electric dipoles, so they flip back and forth about 2.45 billion times per second in the alternating field. That molecular friction produces heat, but only where water, fat or sugar sit. Dry porcelain has almost none of these molecules and stays cool.
Useful: Stir halfway through: microwaves only penetrate a few centimetres, so the middle otherwise stays cold.
Source: de.wikipedia.org