In the fourth episode of the series, legendary nature and cultural photographer Art Wolfe captures the great brown bear with the stunning backdrop of Alaska’s mountains and glaciers, immigrating wildebeests in the plains East Africa, and the hard-to-find gorillas of Uganda.

Deep in the twisted roots of a giant strangler fig tree, hidden from view, lives perhaps the most bizarre nighttime creature of all. The spectral tarsier, tiny primates barely larger than a tennis ball. As darkness falls, a family of these small primates in Sulawesi ventures into the jungle to find food while protecting their babies.

A dynamic journey behind the scenes of the next step in the evolution of telescopes: NASA's James Webb Space Telescope. A new generation has been inspired to design and build this massive instrument, which is 100 times more powerful than the Hubble Space Telescope and will be a veritable time machine, capable of looking back on the origins of our universe and identifying signatures of potential life on planets far outside our solar system". With unprecedented access to the people and technologies that power its creation, including astrophysicists, engineers at Northrop Grumman, and personnel from NASA'S Goddard Space Flight Center and the Space Telescope Science Institute, the operations center for Hubble and Webb, Telescope spotlights the high-stakes mission of building this massive new scientific instrument. The film is a comprehensive look at the dynamic history of 400 years of telescopes starting with Galileo in 1609. The Webb is the next great telescope in society's ongoing mission to see farther into the universe and answer fundamental questions that have haunted mankind from the beginning of time. Directed by Oscar nominated filmmaker Nathaniel Kahn

Just under 200 years ago scientists discovered something profound, that electricity is connected to another of nature's most fundamental forces - magnetism. In the second episode, Jim discovers how harnessing the link between magnetism and electricity would completely transform the world, allowing us to generate a seemingly limitless amount of electric power which we could utilise to drive machines, communicate across continents and light our homes. This is the story of how scientists and engineers unlocked the nature of electricity in an extraordinary century of innovation and invention.

The Arctic is the harshest environment on Earth: little food grows, it's dark for months on end, and temperatures stay well below freezing for much of the year. Yet four million people manage to survive here. Human Planet tells remarkable stories of extraordinary people who make their homes in nature's deep freeze. In springtime, Amos and Karl-Frederik set out across the sea ice with their dogs to catch a real-life sea monster: a Greenland shark! Inuit mussel-gatherers venture underneath the sea ice at low tide for a perilous race against time as they gather their food. And the children of Churchill, Manitoba, set out on the most dangerous trick or treating Halloween in the world: they risk coming face-to-face with deadly polar bears on the streets of their town. Who'll get the tastiest snack?

With much of it covered in ice all year round and with no daylight from October to March, the Arctic Ocean is one of the world's most remarkable oceans. Its home to a multitude of unique life forms, all highly adapted to cope with the extreme and seasonal conditions. The impacts of climate change are more strongly felt here than anywhere else in the world.