The Scoville scale measures the heat of chili peppers and other products containing capsaicin. Capsaicin is a chemical compound naturally found in chili peppers and is responsible for the spiciness or 'hot' sensation you feel when you eat a pepper. Capsaicin is most concentrated in the placenta (the white membranes) of the pepper. That's why the tip of a pepper is often much less hot than the rest of the pepper, as it contains almost no placenta.

The Scoville scale was developed in 1912 by American chemist Wilbur Scoville. Capsaicin is measured in Scoville Heat Units (SHU), which indicate how much sugar water is needed to neutralize the pepper's heat. The scale ranges from zero (no detectable capsaicin) to several million (extremely hot).

The Scoville scale helps people choose peppers that match their taste and tolerance for spiciness. People who regularly eat spicy food can develop a higher tolerance for capsaicin, meaning they experience the burning sensation less quickly. However, some people can remain very sensitive to the substance, even with milder peppers.