The Pyramid of Microwaves is a group of microwaves used for the Series Finale of Is It A Good Idea To Microwave This?. The pyramid consists of six microwaves. Five of them are ones the guys used earlier in season 9 (Marissa and Cindy) and 10 (Gabrielle, Gina and Emily), the sixth one is standing on top of the piramid, which is the microwave the guys use for the experiment (Heather in #299, Shelley in #300). Both microwaves died on their experiments and the other microwaves in the pyramid suffered heavy damage.
Pyramid of Microwaves in #299.
Pyramid of Microwaves in #300.
Remains after the finale.