Odds are excellent that extraterrestrial life exists. So why haven’t we found aliens out in the galaxy? Are we looking in the wrong places? New research shows we should look closer to home, even inside our bodies. It turns out that a lot of our DNA is from a mysterious, nonhuman source. Theoretically, alien microbial life can make the journey to Earth from distant worlds, and scientists are finding some unearthly microbes in our upper atmosphere. Could it be from outer space? Could we be part alien? It’s even possible alien life is already here as digital life forms, hiding inside our technology.

Aliens almost certainly do exist. So why haven't we yet met E.T.? It turns out we're only just developing instruments powerful enough to scan for them, and science sophisticated enough to know where to look. As a result, race is on to find the first intelligent aliens. But what would they look like, and how would they interact with us if we met? The answers may come to us sooner than we imagine, for one leading astronomer believes she may already have heard a hint of their first efforts to communicate

A journey through the cosmos in search of alien life. We seek out planets around distand stars and dive into the oceans of other worlds - seeking an answer to the question: is there anybody out there?

Is mankind alone, or are there aliens out there, either waiting to be discovered, or on their way to find Earth? Professor Brian Cox spends this episode asking such questions, and what he discovers may raise a few eyebrows. He begins by exploring the human race's efforts to find neighbours in outer space, including the launch of two golden discs containing a greeting from Earth in the 1970s; they are still travelling and are now the most distant man-made objects from the planet. Brian also meets members of the Search for Extra-Terrestrial Intelligence, who have been monitoring radio signals for 50 years without success, before discussing the ingredients needed to make an intelligent civilisation with astrophysicist Dr Frank Drake.

The series, depicted by state of the art CGI techniques, and applying the laws of life on Earth to the rest of the galaxy, blends fact with science fiction and conceptualizes what alien life might be like on other planets.
In the prologue, astronomer Didier Queloz makes an appearance to discuss the discoveries of exoplanets and how they are analyzed in the real world. In Episode 1, the fictional world imagined is Atlas, a world with higher gravity than Earth and a thicker atmosphere leading to airborne creatures. In explaining the aliens of Atlas, the episode also explores the handicap principle in insects, and shows a rehabilitative form of falconry as captive falcons are trained to live in the wild.

The world of bugs normally passes beneath our notice, yet shrink yourself to their size, see them in 3D and you’ll enter a world you’d never believe existed. Big Bugs in 3D uses specially developed 3D technology to take the viewer on a global journey, from Mexico and the rainforests of Asia to our own backyards. There are perhaps four and a half million different kinds of bugs sharing the planet with us. They exist in a bewildering variety of forms, some more like creatures from an alien world. Big Bugs asks how and why these creatures have become so successful.