Each kernel of popcorn contains a small amount of water which, when heated, turns to steam. This steam builds pressure. When the pressure reaches about 135 pounds per square inch, the kernel will explode.
Most popcorn comes in two basic shapes. The larger snowflake shape is used in ballparks and theaters, and the smaller mushroom shape is used for confections like caramel corn.
There are six types of maize (pod, sweet, flour, dent, flint, and popcorn) but only popcorn, a.k.a. Zea mays everta, will pop when heated.
This popular myth probably isn’t true. The corn that was grown by the first settlers wasn’t the right variety for popping.
Americans eat so much popcorn — more than fifty popped quarts per person per year — that it could fill the Empire State Building 18 times!
Though popcorn is often thought of as a snack food, it’s also a whole grain. Without added butter, salt, or sugar, it can be a low-calorie, low-fat food.
The Aztecs used to offer “a kind of corn which bursts when parched and discloses its contents and makes itself look like a very white flower” to their water god.
Kernels that are too dry won’t be able to create steam (or pressure) and won’t pop. They’re playfully called “old maids” or “spinsters.”