If you don't want to wade through five paragraphs of senseless drivel to get to the point: Their conclusions: The grape is less like an antenna and more like a

If you don't want to wade through five paragraphs of senseless drivel to get to the point: Their conclusions: The grape is less like an antenna and more like a trombone, though for microwaves instead of sound. When you play a trombone, you push vibrating air into it. The trombone will only sustain vibrations of a particular wavelength—the musical note you hear—depending on where you’ve positioned the slide. Only certain wavelengths, known as standing waves, fit perfectly inside the trombone. As vibrating air of various wavelengths enter the trombone, the standing waves add constructively, while other wavelengths cancel each other out. In other words, the trombone amplifies the standing waves and mutes all others. The grape, incidentally, is the perfect size for amplifying the microwaves that your kitchen machine radiates. The appliance pushes microwaves into the two grape halves, where the waves bounce around and add constructively to focus the energy to a spot on the skin. Both grape halves happen to focus the energy to the same tiny point. That intense energy jostles the atoms and molecules at that spot, heating them up so much that they can no longer hold onto their electrons, which turns them into a plasma—and boom, fireball. tl;dr: constructive EM wave interference from the grape seed.