How do microwaves heat food?

You ask: How microwave heat food?

Inside microwave box live wave-maker called magnetron. It spit invisible waves, cousins of radio waves, into food cave. Now hear real trick: water bits in food are lopsided — one end pull little bit plus, other end little bit minus, like tiny spear with heavy tip. Wave flip direction back and forth, billions of times each heartbeat. Lopsided water bits try to follow, spin this way, that way, this way. All that twisting make water bits bang into neighbors. Banging, jiggling bits — that IS heat. Heat just fast-wiggling stuff. So microwave really heat water hiding in food — and food hide much water, raw meat is three parts water out of four — and water heat rest. Dry bread barely warm; wet stew get hot fast. Plate stay cool because plate hold no water. Cave wisdom: microwave no put heat in food. It shake food own water until food cook itself.