Every year, over a thousand climbers try to reach the summit of Mount Everest, with the annual record for successful attempts currently standing at 633. But of that number, nearly half were Sherpas - the mountain's unsung heroes. Yet the Sherpa community has remained secretive about their nation, culture and experiences living in the shadow of the world's highest mountain. Now, for the first time, they open the door into their world. Without the expertise of the Sherpas, only the hardiest and most skilful climbers would succeed. Every day they risk their lives for the safety of others, yet they seek neither glory nor reward, preferring to stay in the background. Following the stories of four such Sherpas - Phurba, Ngima, Ngima Tenji and Gelu - this film reveals the reality of their daily lives, not just up the mountain, but with their families after they return home.

David Attenborough concludes his epic history of the evolution of flight with an exploration of the highly advanced fliers that dominate our skies today – the extraordinarily diverse skills of the birds, and the sonar-guided precision of the bats. He encounters some of our planet’s most remarkable fliers – from peregrine falcons dive-bombing starlings over Rome, to hummingbirds hovering in the cloud forests of Ecuador. In a spectacular finale, he visits Gomantong cave in Borneo to witness the mass exodus of a million bats.

Rainforests face more threats than ever before, but remain the last stronghold for some truly astonishing animal families. Today we know rainforests are some of the most wondrous and important habitats on Earth. It is the richest habitat on earth, teeming with millions of dramatic plants and animals. From giant landscape gardeners to a whole family supported by a single leaf, there are surprises at every turn.

Welcome to an extreme landscape of rock, ice and snow. We tour the mightiest mountain ranges, starting with the birth of a mountain at one of the lowest places on Earth and ending at the summit of Everest. Find out how some of the most secretive animals rise to the challenge of mountain life. Share one of Earth's rarest phenomena, a lava lake that has been erupting for over 100 years. The same forces built the Simian Mountains where we find troops of gelada baboons nearly a thousand strong. In the Rockies, grizzlies build winter dens inside avalanche-prone slopes and climb the peaks to devour abundant summer moths. In another world first, the programme brings us astounding images of a snow leopard hunting on the Pakistan peaks.

In the final part, Professor Al-Khalili uncovers tales of success and heartache in the story of chemists' battle to control and combine the elements, and build our modern world. He reveals the dramatic breakthroughs which harnessed their might to release almost unimaginable power, and he journeys to the centre of modern day alchemy, where scientists are attempting to command the extreme forces of nature and create brand new elements.

Andrew Marr sets off on an epic journey through 70,000 years of human history. Using dramatic reconstructions, documentary filming around the world and cutting-edge computer graphics, he reveals the decisive moments that shaped the world we live in today, telling stories we thought we knew and others we were never told." Starting with our earliest beginnings in Africa, Marr traces the story of our nomadic ancestors as they spread out around the world and settled down to become the first farmers and townspeople. He uncovers extraordinary hand-prints left in European caves nearly 30,000 years ago and shows how human ingenuity led to inventions which are still with us today. He also discovers how the first civilisations were driven to extremes to try to overcome the forces of nature, adapting and surviving against the odds, and reveals how everyday life in ancient Egypt had more in common with today's soap operas than might be imagined.