Meet Milly, the Puerto Rican chihuahua about to hit the big time as the world's smallest dog.

Milly was born three months ago and has maintained the height of 2½ inches for the last three weeks.

With big bulging eyes, spindly legs and pointy ears we can’t decide if this pooch is adorable – or dare we say it – a bit frightening. The ET of the dog world.

But what is certain beyond doubt is her tiny dimensions. She weighs under six ounces and when she was born, her mouth was so tiny that she had to be fed with an eyedropper.

The world’s official smallest dog is currently Boo Boo, a Chihuahua from Kentucky who weighs in at 5.9 ounces. She has held the record since February 2008, but Milly hopes to bump Boo Boo off the top spot and win a place on the Guinness World Records.

A judge from the Guinness Book of Records is due to travel to Puerto Rico to officially confirm Milly’s size.

But Milly is far from the only tiny dog who has garnered column inches recently. Fans of this sort of thing may remember we ran a piece on Gracie the pint- pug from Norfolk (below). She is just six inches long and is so small she has to wear a kitten harness when she goes for her (equally tiny) walks.

Miniature pup Beyoncé (below) also stole our hearts as soon as we saw her pictures at Stylist HQ. She was born at an animal rescue centre in North California and is not much bigger than a business card.

Let us know what you think on all things tiny pups on Twitter or in the comments section below.

Picture credit: Rex Features