Chili peppers are indigenous to the New World. Native cuisine used them to add heat and flavor to food. European explorers (who called pretty much every new spice "pepper") spread chiles to Europe and Asia, where they were soon integrated into many ethnic cuisines. There are as many kinds of chili pepper as places they're grown, from the mildest paprika pepper to the fiery hot habenero. Heat levels are ranked on the Scoville scale. The crushed red chili flakes used as pizza topping rank between 20,000 and 40,000; richly flavorful ancho goes as low as 1000 Scoville units, and habenero burns out at 200,000.