Most people know that there are three common states of matter: solids, liquids, and gasses. There is a less understood fourth state, called plasma. Wikipedia says is plasma is similar to a gas but some particles are ionized.
You've seen these things in gift stores? They're "plasma lamps".
Three things to know. First, a microwave oven can induce ionization and briefly turn a gas into plasma.
Second, due to the ions, a plasma is electronically conductive, resulting in effects (neon lamp uses plasma).
Lastly, people on the Internet and YouTube will try just about anything with a microwave oven.
In the first YouTube video, the skin of grapes is creates an electric arc that produces a small plasma discharge.
It gets more interesting when the host places a glass over the grapes to capture the plasma (1:45 mark).
In the second video, a match is lit and partially covered (enough to keep oxygen flowing but trap the plasma).
The sustained plasma gets so hot that it breaks the glass. (And I think the gas is toxic, by the way.)
Finally, having nothing to do with plasma, check out the instant art when microwaving a CD or DVD (3.45):
Of course, don't do any if this at home unless you want fire, explosions, and toxic fumes in the kitchen.