Dr. Percy Spencer was working on magnetrons when he discovered his chocolate had melted. He soon realized that microwaves could cook.
Amana put out the "Radarange", the world's first microwave.
Amana put out a smaller version of the Radarange that you can put on a counter.
It was discovered that energy leaked out of microwaves and laws were put in place to make them safer.
Microwaves were cheaper, did more, and sold better. They soon surpassed the amount of dishwashers in the US.
More than 95% of US homes have a microwave.