Popcorn is a variety of corn kernel which expands and puffs up when heated. A popcorn kernel's strong hull contains the seed's hard, starchy core with 14–20% moisture, which turns to steam as the kernel is heated. Pressure from the steam continues to build until the hull ruptures, allowing the kernel to forcefully expand and then cool.
History
Corn was domesticated about 10,000 years ago, in what is now Mexico. Archaeologists discovered that people have known about popcorn for thousands of years. Fossil evidence from Peru suggests that corn was popped as early as 4,700 BC.
Through the 19th century, popping of the kernels was achieved by hand, on stove tops. Kernels were sold on the East Coast of the United States under names such as Pearls or Nonpareil. The term popped corn first appeared in John Russell Bartlett's 1848 Dictionary of Americanisms. Popcorn is an ingredient in Cracker Jack, and in the early years of the product it was popped by hand.
Cooking Methods
Popcorn can be cooked with butter or oil. Although small quantities can be popped in a stove-top kettle or pot in a home kitchen, commercial sale employs specially designed popcorn machines, which were invented in Chicago, Illinois. The invention was the first patented steam-driven machine that popped corn in oil. Previously, vendors popped corn by holding a wire basket over an open flame. At best, the result was hot, dry, and unevenly cooked.
Air-popped popcorn is: 
•	4% water, 
•	78% carbohydrates (including 15% dietary fiber)
•	12% protein, and 
•	4% fat
In a 100 gram reference amount, popcorn provides 382 calories and is a rich source (20% or more of the Daily Value, DV) of riboflavin (25% DV) and several dietary minerals, particularly manganese, phosphorus, and zinc (36-45% DV). B vitamins and other minerals are in appreciable amounts.
Consumption
Popcorn is a popular snack food at sporting events and in movie theaters, where it has been served since the 1930s. Traditions differ as to whether popcorn is consumed as a hearty snack food with salt (predominating in the United States) or as a sweet snack food with caramelized sugar (predominating in Germany).
Popcorn smell has an unusually attractive quality for human beings. This is largely because it contains high levels of the chemicals 6-acetyl-2, 3, 4, 5-tetrahydropyridine and 2-acetyl-1-pyrroline, very powerful aroma compounds that are also used by food and other industries either to make products that smell like popcorn, bread, or other foods containing the compound in nature, or for other purposes.
Popcorn as a breakfast cereal was consumed by Americans in the 1800s and generally consisted of popcorn with milk and a sweetener. Popcorn balls (popped kernels stuck together with a sugary "glue") were hugely popular around the turn of the 20th century, but their popularity has since waned. Popcorn balls are still served in some places as a traditional Halloween treat. 
Cracker Jack is a popular, commercially produced candy that consists of peanuts mixed in with caramel-covered popcorn. Kettle corn is a variation of normal popcorn, cooked with white sugar and salt, traditionally in a large copper kettle. Once reserved for specialty shops and county fairs, kettle corn has recently become popular, especially in the microwave popcorn market. The popcorn maker is a relatively new home appliance, and its popularity is increasing because it offers the opportunity to add flavors of the consumer's own choice and to choose healthy-eating popcorn styles.
Popped sorghum is popular as a snack in India. The popped sorghum is like popcorn, but the puffs are smaller. Recipes for popping sorghum by microwave, in a pot, etc., are readily available online.