A Scoville unit measures the heat level or spiciness of chili peppers and other spicy foods. It's named after American pharmacist Wilbur Scoville, who invented the measurement in 1912. The Scoville scale ranges from 0 (no heat, like a bell pepper) to over 2 million (extremely hot, such as the Carolina Reaper pepper). The measurement is usually determined by tasting and diluting a chili pepper extract with sugar water until the heat is no longer detectable to most tasters.