Summary of Video:

In a microwave oven, resonance between two grapes can ionize the air, creating plasma. The wavelength of 2.45GHz microwaves = 12cm, but the grape's refractive index of ~10 slows down the wave 10x, decreasing the wavelength to about 1.2cm...about the size of a grape. This causes resonance at the center of each grape, just like you can hear "boomy" bass in certain parts of a room.

When two grapes touch, this creates a mode (or standing wave) between them, which builds up enough energy to ionize the air, allowing electrons to flow. If you look at the plasma spectrum, you can see spikes for the sodium (Na) and potassium (K) ions in the grapes.

SCIENCE, BIATCH!