There are thought to be over 5,400 species of mammals living on Earth. They come in all shapes and sizes - from tiny mice to towering giraffes, and scale-covered pangolins to 100-tonne whales.

But despite their differences now, all mammals stemmed from one common ancestor, with the earliest mammal fossils currently thought to date to between 220 and 165 million years ago.

Watch as senior curator of mammals Louise Tomsett explains the surprising similarity between mice and giraffes.

It's all in the neck

Mice and giraffes live drastically different lives – not to mention that giraffes tower over mice by over five meters.

A giraffe's neck is extraordinary long, making up a large part of its height. This allows the animal to reach the leaves of tall trees. But an elongated neck is also integral to the courtship behaviour of 'necking'.