90 million miles away from us is the power that shapes our world - the Sun. We see it shine in the sky above us, but beyond our sight something dramatic is happening - the Sun is going into overdrive. It's more active now that it's been for a decade, sending eruptions of super-heated plasma and vast waves of radiation towards our planet. With the potential to disrupt our lives in dramatic ways. Using the latest satellite images, and the expertise of Britain's leading solar scientists, Kate Humble and Helen Czerski reveal the inner workings of our very own star, and the influence its mysterious cycles of activity have on our planet. They discover why the light reaching us from the Sun can be up to a million years old: they meet the teams who protect us by keeping a round-the-clock vigil on the Sun; and investigate why some scientists think longer term changes in the Sun's behaviour may have powerful effects on our climate.