YouTube user zkossover created a video to show us what actually goes on when you microwave something. To do this, he essentially “built a grid of tiny neon lamps inside a sheet of acrylic.” Continue reading for the video demonstration. Here is why the neon lamps glow:
Microwaves are invisible, so you can’t see them inside microwave oven, but their presence can be detected with neon lamps. The changing electromagnetic field from the microwaves will make charged particles move, and so the electrons in the metal legs will move creating current. This current makes the lamps glow.