Hmmm... I haven't tried myself, but based on an experience, I think that lid's blown off. My Dad's not much of a cook. When I was a teenager and we first got a microwave, he thought he'd soft-boil an egg for my Mom with it. He knew better than to put an egg in the microwave "naked". Unfortunately, his impression of the "right" thing to do was put it in a Pyrex measuring cup filled with water. The ensuing explosion pasted the innards of the oven with semi-cooked egg. It was not forceful enough to fracture the Pyrex cup, but was able to overcome the door seal and pop the oven door open. Based on that, I think the lid of a Tupperware would not have been up to it. Patrick P.S. Some years later, while my parents were living in a temporary apartment after the Oakland Hills fire, he again needed to cook eggs, this time hard-boiled. Having learned his lesson, he chose to use a pot on the stove for a safer, more familiar approach. Water into pot, eggs into water, pot onto the stove. But there was a problem... he didn't have a timer. So, he set the microwave for 20 minutes and started it (empty, on high of course), and went to take a shower, assuming he'd hear the beep when the time expired. During his shower he heard some strange noises, and when he finally reached the kitchen (wrapped in a towel), he was greeted by the local Fire Department, who had been dispatched by the building's central smoke detectors and just extinguished the microwave and the cabinet from which it hung. You should see what he does to Windows. :-)