Chihuahuas are named for the Mexican state of Chihuahua, and the AKC registered its first one in 1904. They're the smallest recognized breed, usually 3 to 9 pounds, with an apple-shaped head, big upright ears and either a smooth or long coat in nearly any color. Shedding is low to moderate, so brushing is a quick weekly job.
Temperament is where Chihuahuas surprise people. Many are bold, alert and attached to one or two favorite people, with plenty of opinions about visitors. That can mean barking, wariness of strangers or snapping if they're handled roughly, so gentle socialization and reward-based training pay off. Dogs vary a lot, and a Chihuahua's age, history and personality matter more than the breed label. Adult Chihuahuas are often calmer and easier to read than puppies.