When you sit down with a bowl of popcorn, you're about to enjoy a snack that is thousands of years old.
The first corn domesticated by the ancient people of Central America was popcorn. Flour corn and sweet corn came millennia later.
Popcorn kernels are smaller and harder than flour corn kernels. They have tough shells that surround a tiny pocket of soft starch and seal in moisture.
At heat, and the kernels act like tiny pressure cookers. The superheated water inside actually liquefies the starch. The temperature rises, the pressure builds, and then...
The liquefied starch froths out, cooling and solidifying in a fraction of a second.
If you look closely, you can see that each popped kernel is made of starch bubbles that are formed by the expanding steam. This is popcorn magnified 250 times.