system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does "popcorn" work? Could we "pop" other grains, like quinoa or rice?
gpt
Grains are usually the actual alive part of the seed that is wet and alive inside a hard dry shell. If you cook it up without burning it one way or another the inside part cooks and expands while the shell around it is hard and dry and dead and stays the same size so the inside part swells up and pops out. 

You have had "popped" rice. It's that puffed up rice they make like, rice crispys out of, or breakfast cereals out of or rice cakes.

Lots of other old people cereals are other puffed grains and a lot of other kid cereals are like, puffed grains that they mash into a paste then make into another shape. Same with things like corn puffs/cheese puffs. snacks like that.