There are several scales for measuring the hotness of chilies. What they actually measure is the capsaicin content, the crystalline, pungent substance that gives chilies their fire. The most popular scale is the Scoville Organoleptic test, which assigns a number between 0 and 300,000 heat units. Habanero pepper's heat, fruity, citrus-like flavor, and floral aroma make it a popular ingredient in hot sauces and spicy foods.