Everyone do yourselves a favor--go to a thrift store and buy a few microwaves. Find a field, string a hundred feet of extension cords from an outlet and start microwaving all the things your not suppose to.

My favorites: Ivory soap--bubbles outward; Grapes--see article; Incandescent lightbulb --lights up; Wine bottle--explodes, do this last

Also lots of things you think would be bad do nothing: spray paint can, soup can, silverware, cup of gas with aluminum foil in it.

The PNAS article has more photos and videos https://www.pnas.org/doi/10.1073/pnas.1818350116

Looking online apparently this damages the magnetron, but no one has found out why precisely. There are some pop-culture explanations that the reflected energy overloads the magnetron and so on, but I don't think anyone has done the parallel what this team has done to actually say what happens to the magnetron.

The PI has a website https://www.aaronslepkov.com/research but nothing new about this stuff there. I'm curious.

We know now why the plasma forms. I hope they're able to explain why the magnetron breaks.

Veritasium has a great video on this: https://youtu.be/wCrtk-pyP0I

> The key, it seems, is cramming the energy present in microwaves into a very tiny space—the point of contact between the objects in question. In your garden-variety microwave oven, microwaves have a wavelength of about 12.5 cm. But adjoining grapes (which are full of water that can absorb said microwaves) can concentrate the energy within into a region where the two spheres touch, which is no more than a couple millimeters wide. This creates a very strong, very condensed electric field at their interface—a pocket of ammo powerful enough to liberate negatively-charged electrons from, say, the salts naturally present in grapes and other fruits.

This is the answer from the article. Not much else is said about the “how” piece

This is the paper cited: https://www.pnas.org/doi/full/10.1073/pnas.1818350116

I'd like to think that some day in the near to mid future microwaving grapes or other spheres will be a way to start a fusion reactor or similar.

pro tip: do not try this on a microwave you want to keep. if you are successful you will likely cause a fire in your microwave. (it is fun, though).