Common varieties of hot peppers include the poblano, serrano, habañero, Cayenne and Anaheim chile pepper. Other spicy options are the cherry pepper, Thai chile, hot banana, jalapeño and Basque fryer. The heat levels of these and other hot peppers are measured via Scoville heat units (SHU), with the tame bell pepper registering zero; the mercilessly fiery Carolina reaper ranges between 1.6 million to 2.2 million SHU.
Originally long, slender and tapered, the Cayenne pepper is found in dried form in almost every grocery store, and is a common ingredient in many Tex-Mex dishes, particularly chiles. It is relatively spicy, registering between 30,000 and 50,000 SHU.
The large, heart-shaped poblano is milder in heat and turns dark brown with maturation, a process that transforms it into an ancho chile. When smoked and dried, the poblano becomes a chipotle, a key ingredient in many mole sauces.
The serrano is a short, slender pepper that is hotter when shorter and red or yellowish orange when ripened. Featuring consistently in both Mexican and Thai cuisine, the serrano registers at between 6,000 to 23,000 SHU. Among the most commonly available peppers, habañeros are likely the hottest, typically coming in small, bulbous shapes. Popular in Mexican and Caribbean sauces, the habañero has a fruity note following its heat, the latter sometimes being in excess of 350,000 SHU.