How does a microwave oven work?

How was the microwave oven accidentally invented? How do microwaves work to cook everything from frozen pizza to popcorn? Why should you never put metal in a microwave? Your smart elementary school kid will learn about all this and more, and there's more free activities at www.WhoSmarted.com! See omnystudio.com/listener for privacy information. See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.