TV series
Horizon tells amazing science stories, unravels mysteries and reveals worlds you've never seen before.
Availability
Checked Jul 22, 2026
Horizon premiered February 4, 1964. We don't have a confirmed streaming, rental or purchase option yet.
Horizon tells amazing science stories, unravels mysteries and reveals worlds you've never seen before.
Choose an episode, then use the watch options above for the show.
Episode 1
Top brain surgeon Henry Marsh is facing his own life-threatening diagnosis. He reveals the huge risks and emotional impact of a job filled with difficult life-and-death decisions. This heartwarming portrait of an eccentric surgical hero facing the end of his life reveals the truth about brain surgery and its human impact, with devastating emotional power and life-affirming honesty.
Where to watch Horizon
Episode 2
Virologist Dr Chris van Tulleken embarks on a global investigation into the hunt for the pathogen that could trigger the next pandemic and the cutting-edge science developed to tackle it. Known only as "Disease X", it is shrouded in uncertainty. Its origin is unknown, how it could spread is unclear, but its impact could be much more severe than Covid-19. To uncover what Disease X might be, where it could emerge and what traits it needs to spread, Chris follows the paths of past deadly viruses. He visits the ground zero of the Nipah virus in Malaysia, which inspired the film Contagion. He also heads to the front line of the ongoing bird flu outbreak in American dairy cattle in California.
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Episode 3
Theoretical physicist Professor Jim Al-Khalili goes on a journey through 600 million years of evolution to uncover how the human brain, the most complex structure known in the universe, came to exist. With some 100 billion neurons and over 100 trillion connections - more than all the stars in the Milky Way - the human brain is one of nature's greatest achievements. But how did something so incredibly sophisticated evolve from its simple beginnings?
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Episode 4
Jim watches primates in action to see how they tackle survival challenges, revealing the clever tricks that shaped the brain's thinking. But the real breakthrough came when brains learned to be social. Teaming up with his wife, Jim investigates how relationships and friendships made people more intelligent. With AI getting smarter by the day, Jim wants to know what makes biological brains so special. Through scans, fossil discoveries and cutting-edge research, he uncovers what makes the brain so hard to emulate.
Where to watch HorizonEpisode information updated Jul 24, 2026
Available now in United States
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