We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

Join the Mars rovers Spirit and Opportunity for an awe-inspiring journey to the surface of the mysterious red planet. Through the eyes of these two intrepid, death-defying rovers, and with NASA scientists and engineers at your side, you’ll see Mars in a way no one ever has before. You’ll feel what it is like to stand on the startling surface of the planet that’s intrigued mankind for eons. And you’ll uncover its ultimate mystery: Is there life on Mars? Roving Mars – it’s the ride of a lifetime.

In this documentary we moved to Ancient Egypt to learn their vision of the world, life and death, gods and magic. For the ancient Egyptians, the Nile was the main connection between their lives and an infinite supply of provisions. But its waters hid an underworld of darkness and mystery for its first settlers. The Nile was one the spiritual paths that combined life and death, the real world and the underworld.

We feel it every moment of our lives but for physicists, gravity is the longest running unsolved mystery of the universe. Why do all objects that have mass pull on one another? Cutting-edge theories are proposing unexpected answers: Gravity could be another force in disguise, a thermodynamic mirage, or even, a shadow of a hidden holographic universe. If so, the force that holds us to the surface of the earth, and holds the earth in orbit around the sun, may be a trick of the mind. We feel it, but it may not be real. Is Gravity an Illusion?

Every cosmologist and astronomer agrees: our Universe is 13.7 billion years old. Using cutting-edge technology, scientists are now able to take a snapshot of the Universe a mere heartbeat after its birth. Armed with hypersensitive satellites, astronomers look back in time to the very moment of creation, when all the matter in the Universe exploded into existence. It is here that we uncover an unsolved mystery as old as time itself -- if the Universe was born, where did it come from? Meet the leading scientists who have now discovered what they believe to be the origin of our Universe, and a window into the time before time.