There are 5 different types of corn (sweet, flint, dent, waxy and popcorn). From these types only popcorn is the one that pops.
After expansion (popping), popcorn can have two different shapes. The first one looks like a small cloud and is called “butterfly” and the other looks like a small ball and is called “mushroom”
But what is that, which really makes popcorn pops? The answer is “water”. The basic composition of popcorn seeds are carbohydrates (mainly starch), protein, fat and water. The water is stored in a small vessel of soft starch in every seed. As the seed heats up, the temperature of the water rises, so is its’ pressure to the outside environment.
The hard surface of the starch holds the water pressure as long as it can. But as soon as the surface breaks, the water is released and the popcorn seed explodes. The soft inner starch breaks in this causes the seed to turn its’ inside out. The internal moisture of the seed is released in the form of steam and this is finally what causes popcorn to pop.