The smallest breed of dog is the Chihuahua, which typically weighs between 2 to 6 pounds and stands around 6 to 9 inches tall at the shoulder. Originating from Mexico, Chihuahuas are known for their lively personalities and strong bond with their owners. Despite their tiny size, they often exhibit bold behaviors and can be quite protective. Their unique characteristics and adaptability make them popular companions. It's important for owners to provide proper training and socialization due to their sometimes aloof nature toward strangers.