Water plants create some of the most beautiful, bizarre and important habitats on earth. To hold on in torrents, plants use a kind of superglue. Some are armed with vicious weapons to fight titanic battles for space. Others form perfect spheres and escape from animal enemies by rolling. Where nutrients are washed away, plants turn into hunters of animals, laying traps and even counting to ensure their success.
In this episode we explore those watery worlds with David Attenborough, from Croatia to Brazil, from Colombia to Thailand, the brilliantly coloured flowers smother lakes, and in one magical river in Brazil, the water bubbles like champagne as plants create the atmosphere itself.

Dr Hannah Fry explores a paradox at the heart of modern maths, discovered by Bertrand Russell, which undermines the very foundations of logic that all of maths is built on. These flaws suggest that maths isn't a true part of the universe but might just be a human language - fallible and imprecise. However, Hannah argues that Einstein's theoretical equations, such as E=mc2 and his theory of general relativity, are so good at predicting the universe that they must be reflecting some basic structure in it. This idea is supported by Kurt Godel, who proved that there are parts of maths that we have to take on faith.
Hannah then explores what maths can reveal about the fundamental building blocks of the universe - the subatomic, quantum world. The maths tells us that particles can exist in two states at once, and yet quantum physics is at the core of photosynthesis and therefore fundamental to most of life on earth - more evidence of discovering mathematical rules in nature. But if we accept that maths is part of the structure of the universe, there are two main problems: firstly, the two main theories that predict and describe the universe - quantum physics and general relativity - are actually incompatible; and secondly, most of the maths behind them suggests the likelihood of something even stranger - multiple universes.
We may just have to accept that the world really is weirder than we thought, and Hannah concludes that while we have invented the language of maths, the structure behind it all is something we discover. And beyond that, it is the debate about the origins of maths that has had the most profound consequences: it has truly transformed the human experience, giving us powerful new number systems and an understanding that now underpins the modern world.

Whales have long been a profound mystery to us. They live in a world so removed from our own that we can barely imagine their lives. Their environment is different, their senses are different, their relationships are different. How might such almost alien creatures see the world?, Narrated by David Attenborough.

What is the universe made of? If you answered stars, planets, gas and dust, you'd be dead wrong. Thirty years ago, scientists first realized that some unknown dark substance was affecting the way galaxies moved. Today, they think there must be five times our understanding of the universe and the nature of reality itself has drastically changed over the last 100 years - and it's on the verge of another seismic shift. In a 17-mile-long tunnel buried 570 feet beneath the Franco-Swiss border, the world's largest and most powerful atom smasher, the Large Hadron Collider, is powering up. Its goal is nothing less than recreating the first instants of creation, when the universe was unimaginably hot and long-extinct forms of matter sizzled and cooled into stars, planets, and ultimately, us. These incredibly small and exotic particles hold the keys to the greatest mysteries of the universe. What we find could validate our long-held theories about how the world works and what we are made of -- or, all of our notions about the essence of what is real will fall apart.

Time i s a concept which is so familiar, and yet recent discoveries have revealed it to be far stranger than we could have possibly imagined. In the final programme in the series, Brian explores the enigma of time - a phenomenon we take for granted but which is one of the biggest mysteries in the universe. He recalls highlights from his TV series that touch upon this conundrum.

Psychopaths have long captured the public imagination. Painted as charismatic, violent predators lacking in all empathy, they provide intrigue and horror in equal measure. But what precisely is a psychopath? What is it that drives them to cause harm, even kill? And can they ever be cured? The film also features a series of candid interviews with prison inmates who not only describe their crimes but why they think they committed them.
'What Makes a Psychopath?' explores not only how each individual's crimes were shaped by their own life experiences, but also gives an insight into how these people think and behave. Working with the world's experts in the field, the film sheds light on the biological, psychological and environmental influences that shape a psychopath. And it looks to the future, with ground-breaking research that suggests a lifetime of incarceration is not the only option to manage violent and dangerous psychopaths.