This is something I remember doing when I was in third or fourth grade. The air bubbles inside the marshmello gain more kentic engery when heated in the microwave, making the marshmellow grow... and grow... and grow. They're kind of nasty to eat tho, so just be warned.
How to do it:
Step 1: Stick a marshmellow in the microwave
Step 2: Set the microwave for over a minute and turn it on
Ok, so maybe you didn't need a step by step annalysis of that. Have fun.
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