Why do Peeps blow up in the microwave?

Aimee J. asks, "Dr. Volt, why do Peeps^TM blow up in the microwave?"

Egad, Aimee! What sort of dastardly, diabolical experiments are you up to? I'm impressed; clearly you are quality material for my Mad Scientist Training Academy this summer.

Peeps^TM, like many living organisms, are primarily composed of water. Microwaves function as they do because the wavelengths of electromagnetic radiation they emit (with wavelengths on the order of ~ 10^-6 meters, term micrometers or microns, hence the name microwave) are wavelengths easily absorbed by water molecules. When the water molecules absorb the microwaves they gain energy, and as all the water molecules in an object gain energy the temperature of the object as a whole increases.

The marshmellow-based tissue of a Peep^TM consists primarily of water and sugar, which when whipped up into a foam contains many tiny air bubbles. As the water heats up it in turn heats up the air pockets which then expand, causing the entire structure of the Peep to expand with it.

For more information check out Peep^TM Research Headquarters. Do these guys know Mad Science or what?