Question: What does every kernel of popcorn contain?
About the article "Popcorn", section "Popping mechanism".

Candidate passages:
This is a list of popcorn brands.
Popcorn also known as popping corn, is a type of corn (maize, "Zea mays var.
everta") that expands from the kernel and puffs up when heated.
Popcorn is able to pop because its kernels have a hard moisture-sealed hull and a dense starchy interior.
Pressure builds inside the kernel, and a small explosion (or "pop") is the end result.
Some strains of corn are now cultivated specifically as popping corns.
Microwave popcorn is a convenience food consisting of unpopped popcorn in an enhanced, sealed paper bag intended to be heated in a microwave oven.
In addition to the dried corn the bags typically contain solidified cooking oil, one or more seasonings (often salt), and natural or artificial flavorings or both.
With the many different flavors, there are many different providers. 
Scheduled annually on the first Saturday after Labor Day, the Valparaiso Popcorn Festival is an all day event held in the downtown area of Valparaiso.
Included in the festivities are a 5-mile run (the Popcorn Panic), a block-long kiddie run (the Lit'l Kernel Puff), 5-mile walk, live entertainment, hundreds of food and craft vendors and the nation's 2d oldest Popcorn Parade.
Parade designers are encouraged to use popcorn in their float designs.
Early Festivals even offered free popcorn to every attendee. 
Popcorn seasoning can refer to a variety of seasonings that are used to add flavor to popcorn.
In the United States, popcorn seasoning is mass-produced by several companies for commercial and consumer use.
Popcorn seasonings may be used to enhance the flavor of popcorn, and some are used to add a buttery flavor to popcorn.
Significant amounts are often used to ensure the adequate flavoring of popcorn, due to popcorn's low density.
It is also sometimes utilized to add coloring to popcorn.
Some popcorn seasoning may contain monosodium glutamate.
Some specialty products exist in unique flavors, such as chocolate and bubble gum.
Dry popcorn seasoning may be finely granulated to enable even dispersion upon popcorn.
Some oils used to cook popcorn contain popcorn seasonings mixed within the oil, and may be referred to as popcorn seasoning oils or liquid popcorn seasoning.
Common homemade popcorn seasoning ingredients include salt and melted butter.
Some popcorn seasoning products may be referred to as popcorn salt. 
Popping results are sensitive to the rate at which the kernels are heated.
If heated too quickly, the steam in the outer layers of the kernel can reach high pressures and rupture the hull before the starch in the center of the kernel can fully gelatinize, leading to partially popped kernels with hard centers.
Heating too slowly leads to entirely unpopped kernels: the tip of the kernel, where it attached to the cob, is not entirely moisture-proof, and when heated slowly, the steam can leak out of the tip fast enough to keep the pressure from rising sufficiently to break the hull and cause the pop.
Producers and sellers of popcorn consider two major factors in evaluating the quality of popcorn: what percentage of the kernels will pop, and how much each popped kernel expands.
Expansion is an important factor to both the consumer and vendor.
For the consumer, larger pieces of popcorn tend to be more tender and are associated with higher quality.
For the grower, distributor, and vendor, expansion is closely correlated with profit: vendors such as theaters buy popcorn by weight and sell it by volume.
For both these reasons, higher-expansion popcorn fetches a higher profit per unit weight.
Popcorn will pop when freshly harvested, but not well: its high moisture content leads to poor expansion and chewy pieces of popcorn.
Kernels with a high moisture content are also susceptible to mold when stored.
For these reasons, popcorn growers and distributors dry the kernels until they reach the moisture level at which they expand the most.
This differs by variety and conditions, but is generally in the range of 14–15% moisture by weight.
If the kernels are over-dried, the expansion rate will suffer and the percentage of kernels that pop at all will decline.
When the popcorn has finished popping, sometimes unpopped kernels remain.
Known in the popcorn industry as "old maids", the kernels don't pop because they do not have enough moisture to create enough steam for an explosion.
Rehydrating prior to popping usually results in eliminating the unpopped kernels.
Popcorn varieties are broadly categorized by the shape of the kernels, the color of the kernels, or the shape of the popped corn.
While the kernels may come in a variety of colors, the popped corn is always off-yellow or white as it is only the hull (or pericarp) that is colored.
"Rice" type popcorns have a long kernel pointed at both ends; "pearl" type kernels are rounded at the top.
Commercial popcorn production has moved mostly to pearl types.
Historically, pearl popcorns were usually yellow and rice popcorns usually white.
Today both shapes are available in both colors, as well as others including black, red, and variegated.
Commercial production is dominated by white and yellow. 
In mathematics, the term simple is used to describe an algebraic structure which in some sense cannot be divided by a smaller structure of the same type.
Put another way, an algebraic structure is simple if the kernel of every homomorphism is either the whole structure or a single element.
Some examples are:  A group is called a simple group if it does not contain a non-trivial proper normal subgroup.
A ring is called a simple ring if it does not contain a non-trivial two sided ideal.
A module is called a simple module if does not contain a non-trivial submodule.
An algebra is called a simple algebra if does not contain a non-trivial two sided ideal.
The general pattern is that the structure admits no non-trivial congruence relations.