Jean Anthelme Brillat-Savarin famously wrote that a meal without cheese is like a beautiful woman missing an eye. Though I certainly appreciate a good cheese course, even less imaginable to me is Mexican food without chillis. Now found all over the world (more ubiquitous than any other spice), chillis have been cultivated in Mexico for almost six millennia. Whether dried, green, smoked, hot, fresh, red, or mild, chillis have a place in nearly all of my favorite Mexican dishes. (A note on the spelling: called chile in Spanish and chili in the United States, a less ambiguous spelling is chilli, the original Nahuatl (an Aztec dialect) word.)

Not only do chillis add something to food that nothing else can, but they are also bizarre culinary specimens. I poked around in a few of my best general- and Mexican-food reference books to learn a little more about this strange fruit. My first question centered around the main characteristic of chillis, their pungency.

Bitter, salty, sweet, sour, and savory (or umami): the basic tastes. These five, each with taste buds devoted to it alone, combine to form the flavor of everything we eat. Right? But what about chile con carne and pico de gallo? Looking beyond Mexican food, what about Thai green curry or Indian vindaloo? In other words, what about hot and spicy?

Neither "hot" nor "spicy" gets included with the five basic tastes because the perception of a dish as hot corresponds with pain receptors, not taste buds. We could never discern the difference between taste and pain, though, because every taste bud has a pain receptor wrapped around it.

This also accounts for why some of us can't stand spicy food and others relish it: some people have as much as 100 times the number of taste buds as other people--and therefore 100 times the number of pain receptors. Think twice about calling a spice-hater a picky or unadventurous eater—that person probably can taste better than you can!

The main culprit for hot spice in food is a chemical called capsaicin, found in the white membranes (not the seeds, as many think) of chillis. In its pure form, capsaicin is lethal even to inhale. Nature didn't intend for humans to love chillis: they contain capsaicin to protect themselves from consumption (and destruction of the seeds) by mammals. The hotness of chillis varies according to how much capsaicin each contains.