[revertmean]

> water molecules in food start to vibrate producing heat

That isn't really how microwaves work. Or, perhaps, that's how all radiation heat things work. It's any molecule that will absorb radiation of that frequency. So your grill works the same way, just at a different frequency. At microwave level, it's water, fats, all sorts of things. The difference is really the stuff that doesn't absorb at those frequencies.