Popcorn - What Makes it Pop? Popcorn is a whole grain maize product -- it's grown extensively in the corn belt states of the U.S., where the majority of popcorn sold worldwide is grown. It resembles corn-on-the-cob in appearance and cultivation, although only popcorn kernels have the ability to pop. Popcorn can be ear-harvested, where the whole ear of corn is cut and stored for eight-12 months, until the moisture levels in the kernels reach optimum levels. At this point, the kernels are stripped from the cobs and graded to eliminate ones that are too small to pop efficiently. Alternatively, popcorn can be harvested by the combine method where the corn cobs are picked and shelled simultaneously. The kernels are then dried with hot forced air, packed and distributed for sale. Popcorn's ability to pop lies in the fact that the kernels contain a small amount of water stored in a circle of soft starch inside the hard outer casing. When heated, the water expands, creating pressure within, until eventually the casing gives way, and the kernels explode and pop, allowing the water to escape as steam, turning the kernels inside out. Although the early Indian corn carried no popping guarantee, popcorn brands today vow at least 99 percent of the kernels will pop. The key is a constantly improved product. Throughout the years, popcorn processors have implemented significant hybrid popcorn seed research to continually enhance their product.