Our perfectly calibrated, breathing planet. For those privileged few who have seen Earth from space, the very first thing they notice is the thin blue line of atmosphere that clings to our planet and sustains life. The story of how the Earth creates and regulates that oxygen is mind-blowing. From snowflakes in the arctic to plankton, desert sandstorms, and rivers in the sky; an incredible chain of connections reveal just how incredible our home is. Everything connects so life and planet breathe together.

Earth protects itself from the sun. The David and Goliath story of Earth's relationship with its greatest threat, our seemingly benign Sun. The Sun is the big violent boss of the Solar System, throwing out devastating particles and energy. Without several shields, one generated by our unique planetary core, another by our atmosphere, and a third by our interconnected weather systems… life on Earth would never have survived.

Earth gives birth to life. The building blocks of life are common across the universe, but life is rare. What's so special about Earth that it emerged here? Only here on Earth have we found the elixir of life; water in its three forms. But for life to emerge this isn't enough… huge tides created by the proximity of our perfect Moon, plate tectonics, volcanoes and lightning mean the Earth is a dynamic planet. It's a huge planetary chemical experiment, a bubbling cauldron that transforms dead minerals into deoxyribonucleic acid (DNA); the code for all life.

The freak accident behind complex life. All life on earth started as single cell bacteria and stayed like that for 2 billion years. Successfully spreading across the planet. So even if we do find alien life, what are the chances of that life being complex – like us? Vanishingly rare… on our strange rock, it's all down to a freak event, which accidentally happened when one cell ate another to create a kind of cellular power pack: mitochondria. This almost miraculous event transforms earth into a complex interconnected food web based on a competition for food. And at the top of the pyramid sits us humans.

There's no place like home. We wrap up the series with the story of NASA's most experienced female astronaut, Peggy Whitson, as she returns home to earth. We might possibly be the only intelligent life in the universe. Life is rare, complex life rarer, and intelligent life may be an evolutionary bad idea or dead end that is rarer still… and that means that it's possible that we humans may be the only thing in this huge and amazing universe that can appreciate its strangeness with awe and wonder.