The National Science Foundation conducted a study and found that only 33 percent of Americans know what a molecule is.

Pictured above is a water molecule, two little hydrogen atoms attached to an oxygen atom. Note that the hydrogen atoms aren’t directly opposite each other, but arranged more like Mickey Mouse’s ears.
When water molecules are placed in an alternating electromagnetic field, the ears are pulled one way, then the other. Do it at just the right speed, 2.45 gigahertz, or two-billion-four-hundred-fifty-thousand times per second, the natural ‘resonance’ of water, and a lot of friction is built up resulting in heat. That’s how microwave ovens work.