Nothing can match the frequent flyer miles the Doctor has put on the TARDIS. His trusted time machine, which was developed by the Time Lords, has taken the Doctor and a host of traveling companions from the end of the universe to the end of time and back. It possesses the ability to appear at any time and in any place throughout the known universe, although the TARDIS does seem to end up on Earth in Britain quite a bit. If you've ever wondered what makes the TARDIS tick, these five facts will help unlock some of its mysteries from "Dr. Who."

Chameleon Circuit:

A chameleon circuit allows the TARDIS to assume any size and shape to blend into its surroundings. The only problem is the circuit malfunctioned after a trip to 1960s London. This leaves the TARDIS locked into the shape of a London police box. The Doctor has made efforts in various episodes to repair the circuit, but finally gave up and accepted piloting around a police box.

Spacious Interior:

Just like a reverse onion, the inside of the TARDIS is bigger than the outside. Despite appearing no larger than a phone booth from the exterior, the TARDIS is revealed to be a massive ship once The Doctor and his traveling companions enter into it. The exact dimensions have never been specified, but the TARDIS contains a large number of rooms and corridors.

Organic Product:

The TARDIS, like other Time Lord ships, is grown organically instead of being constructed. It also becomes fully functional through biological means. A TARDIS must receive the biological imprint of a time lord to operate at full capacity. That would make the Doctor one of the first forerunners of the "going green" movement, and it kind of puts a new spin on the whole "bio-fuel" thing, doesn't it?

A Living Ship:

This is no inanimate object. A soul inhabits the TARDIS, which means it is alive as much as the Doctor himself. He found that out in an episode when the soul of the TARDIS transferred to a humanoid female for a brief period of time. It has a mind of its own and takes the Doctor where he is needed, instead of where he wants to go. It's not quite "fait accomplis," but it's nice to know that the Doctor isn't wandering through time aimlessly.

Universal Translator:

The Doctor gets into some pretty wild situations, and in the process he comes into contact with lots of different people (and non people, for that matter). Fortunately for the Doctor, communicating with alien races is no problem onboard the TARDIS. It is equipped to translate any alien language so that the Doctor and his traveling companions can understand their words in their own language. It's kind of like the UN translators, only with less petty squabbling!