Fruit varies substantially in shape, pericarp thickness, color and pungency. Most cultivated peppers belong to one of two major groups. The Grossum group includes the globose, mild-flavored, sweet peppers. The Longum group includes the "hot" chili and cayenne peppers, characterized by their extreme pungency. The pungency of hot peppers is caused by the compound capsaicin and is rated in terms of "Scoville heat units." Jalapeńo peppers range from 2,000 to 6,000 units, whereas the bell peppers lack capsaicin and are rated zero on the Scoville heat unity scale of pungency.