Overview: Viewed from space, our blue planet seems as familiar as a long-time friend – so familiar that we forget how extraordinary it really is. As far as we know, our world is unique in the universe, defined by three elements, Air, Land and Water. Each element has its own special properties and phenomena and is home to myriad lifeforms that have infiltrated every habitat, from the deepest oceans to the tiniest nooks and crannies.