Despite popular belief, the word chile refers to any pepper, not just a hot one. In fact, chiles can range from sweet to meaty, from mild to extremely spicy. The chemical compound capsaicin is what makes the hot varieties so fiery, and some kinds of peppers don’t have any capsaicin at all.

Those that do contain capsaicin, pack the compound in the chile’s interior white walls and in the seed pods. (Turns out the seeds themselves are only spicy by association!)

The Scoville scale measures how much capsaicin is in a variety of chile; in other words, just how hot it is.