Sex is a simple word for a very complex set of desires. It cuts to the core of our passions, our wants, our emotions. But when it goes wrong, it can be the most painful thing of all. Professor Alice Roberts looks through 45 years of Horizon archive to see how science came to understand sex, strived to solve our problems with it, and even help us to do it better. Can science save the day when sex goes wrong?

David Attenborough investigates arguably the most important issue of the 21st century - the future of life on Earth

David Attenborough investigates arguably the most important issue of the 21st century - the future of life on Earth

David Attenborough investigates arguably the most important issue of the 21st century - the future of life on Earth

David Attenborough investigates arguably the most important issue of the 21st century - the future of life on Earth

Documentary which unravels the story of notorious performing whale Tilikum, who - unlike any orca in the wild - has taken the lives of several people while in captivity. So what exactly went wrong?

Professor Richard Fortey travels across the globe to find the survivors of mass extinction events

How some species survived the ice age that began 2.8 million years ago.

In episode two, Fortey focuses on the 'KT boundary'. 65 million years ago, a 10 km diameter asteroid collided with the Earth and saw the end of the long reign of the dinosaurs.

It is estimated that 99 per cent of species have become extinct and there have been times when life's hold on Earth has been so precarious it seems it hangs on by a thread.

Series in which mathematician Marcus du Sautoy explores the stories behind some of the world's most familiar and influential scientific diagrams.

David Attenborough narrates a natural history of the oceans

Wildlife documentary looking in particular at the elusive Blue whale, and following a Grey Whale and her newborn calf as they are pursued by Killer whales

2007. A thousand metres down, in the twilight zone, animals play a constant game of hide and seek.

2007. An unfortunate shoal of sardines is first attacked by three-metre-long striped marlin with metre-long, needle-sharp javelins on their heads. The commotion attracts juvenile yellowfin tuna and then a 14-metre Sei whale scoops up the remains.

2007. In winter the temperature drops to below -50 degrees centigrade and in Antarctica most animals escape the weather. But emperor penguins stay put and huddle together, incubating their eggs and rearing their chicks in the worst weather on the planet. Weddell seals also remain, keeping their breathing holes open by scraping away the ice with their teeth.

This next instalment is about coral reefs, which are so crowded that they play host to a perpetual battle for space, even among the coral itself. It starts life as a larva that becomes a polyp. Having multiplied, it hardens into a limestone skeleton and grows to form a reef. As the community flourishes, animals develop relationships with one another and such a place can feature a huge variety of ocean life.

This programme surveys the effects of the seasons on the world's temperate seas — the most productive on Earth.

2007. A huge tidal wave, sweeps 200 miles inland up the River Amazon. It's an event that only happens on key days each month, when the moon and sun combine their gravitational pull to maximum effect. The force of the wave shatters immense rainforest trees.

2007. Each year the entire population of green turtles that live off the coast of Brazil undertakes a massive 5,000-mile migration to the tiny seven-mile-wide island of Ascension, lost in the middle of the Atlantic.

In a three-part series, Dr Adam Rutherford tells the extraordinary story of the scientific quest to discover the secrets of the cell and of life itself. Every living thing is made of cells, microscopic building blocks of almost unimaginable power and complexity. This episode explores how scientists delved ever deeper into the world of the cell, seeking to reveal the magic ingredient that can spark a bundle of chemicals into life.

In a three-part series, Dr Adam Rutherford tells the extraordinary story of the scientific quest to discover the secrets of the cell and of life itself. Every living thing is made of cells, microscopic building blocks of almost unimaginable power and complexity. The final part reveals how our knowledge of cells has brought us to the brink of one of the most important moments in history.

The film is an unvarnished account of the scientists who dared to discover the secret of life - told through fascinating and revealing archive - in their own words.

A portrait of the spectacular, dynamic nature of Britain over the course of one year.

Spring arrives, marking the start of an epic race for life where timing is everything.

A portrait of the spectacular, dynamic nature of Britain over the course of one year. In the midst of winter, time-lapses show a magical country shrouded in frost and mist.

The fading sun brings a change to Britain: a time of storms and unpredictable weather.

The Great Rift Valley provides the stage for an epic battle between trees and grass - its course influenced by volcanic eruptions, landscape and rainfall. On its outcome rests the fate of Africa's great game herds.

In this major three-part series, Chris and Xand van Tulleken uncover the latest secrets of our bodies.