People have been fascinated by popcorn for centuries. Some Native Americans believed that a spirit lived inside each kernel of popcorn. When heated, the spirit grew angry and would eventually burst out of its home and into the air as a disgruntled puff of steam. However, A less charming but more scientific explanation exists for why popcorn pops.

A popcorn kernel is a cereal grain (seed) scientifically known as Zea mays everta. It is made up of four major physical structures:
(1) The Pericarp (seed coat or outer hull): a hard outer thin covering.
(2) The Endosperm: starchy part that forms the bulk of the kernel and consists almost entirely of starch along with smaller amounts of protein, fat, minerals and water. This water plays an important role in the popping process of popcorn.
(3) The Germ (embryo): The rudimentary (partially developed) plantlet within the seed. This is the structure that develops and grows into a new plant when it is planted.
(4) Tip Cap: the part where the kernel joins (attaches to) the cob.

Out of these four above mentioned elements, three main elements play crucial role to produce popcorn kernels that are good for popping. Those three elements are: the percentage of water content; hard, undamaged, water impermeable shell; and a starchy center.

However, popcorn pops mainly due to the starchy part (the endosperm) that contains water inside it. Each of the kernels has a very tiny amount of water inside that, when heated to a high temperature, turns to steam. When it turns to steam, it expands and causes pressure to build up inside the kernel (like if you blow up a balloon with too much air). This pressure gets higher and higher, until eventually the hard shell of the corn explodes out with a popping sound, and turns the kernel inside out, making popped corn, or popcorn!