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.