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I think mikewith's answer misunderstands my question. I'm talking of 'popcorn', that is, old-fashioned raw popping corn kernels. The science of why popcorn pops is an established answer (try typing 'why does popcorn pop? into Google) but I wondered what it actually looked like and whether anyone had filmed the moment of popping.
The answer he refers to is 'popping candy', which I think is what used to be called 'Space Dust'. When you put that powder on your mouth, you got a prickle of miniature sparkling on your tongue, as though you were eating soda water!