A tiny dog from America called Boo Boo has been named as the smallest pooch in the world. At just four inches (10.16cm) tall, the Chihuahua is the world’s smallest dog in height, according to the Guinness Book of World Records. Boo Boo’s owner, Lana Elswick, breeds Chihuahuas, and said Boo Boo was the size of her thumb when she was born. Elswick told an American newspaper that the Chihuahua is a total diva, and her favourite food is crisps. Boo Boo hasn’t got much bigger since being born a year ago, weighing just 42.5 grams (1.5 ounces).