Ever wonder what's happening inside your head? From dreaming to anxiety disorders, discover how your brain works with this illuminating series. The first episode looks at how memory works and examines the way in which the brain stores, processes, and retrains memories. It also looks at the ways in which memory can fail and discusses how memories can warp over time. It talks to neuroscientists and a memory champion who explains her techniques.

Our universe reveals itself in ways we’ve never seen before, thanks to new discoveries in astrobiology. Today, the advent of cutting-edge observational instruments is shedding light on amazing facts about life and the universe. NASA's next-generation space telescope TESS (Exoplanet Survey Satellite) has begun its search for Earth-like planets belonging to other star systems. How many of these 'exoplanets' can host life, and what kind of life forms can evolve in these environments?

In the last in the series Professor Jim Al-Khalili explores how studying the atom forced us to rethink the nature of reality itself. He discovers that there might be parallel universes in which different versions of us exist, finds out that empty space isn't empty at all, and investigates the differences in our perception of the world in the universe and the reality.

Julian Richards investigates the impact of the Vikings in Britain. This edition focuses on the archaeological trail left by the Vikings as they travelled from Norway along the sea road to Dublin. Settlements, a boat burial and evidence of trading have been discovered on the Scottish isles, and silver hoards found in Ireland suggest that Dublin was not only wealthy and important, but also a centre for trade in slaves.

Mammals' ability to learn new tricks is the key to survival in the knife-edge world of hunters and hunted. In a TV first, a killer whale off the Falklands does something unique: it sneaks into a pool where elephant seal pups learn to swim and snatches them, saving itself the trouble of hunting in the open sea. Slow-motion cameras reveal the star-nosed mole's newly-discovered technique for smelling prey underwater: it exhales then inhales a bubble of air ten times per second. Young ibex soon learn the only way to escape a fox - run up an almost vertical cliff face - and young stoats fight mock battles, learning the skills that make them one of the world's most efficient predators.

A humpback whale mother and calf embark on an epic journey from tropical coral paradises to storm ravaged polar seas. Newly discovered coral reefs in Indonesia reveal head-butting pygmy seahorses, flashing 'electric' clams and bands of sea kraits, 30-strong, which hunt in packs. Elsewhere plagues of sea urchins fell forests of giant kelp. Huge bull fur seals attack king penguins, who despite their weight disadvantage, put up a spirited defence.