It's invisible, ever-present, and essential, with a chemical profile encompassing billions of years of history. In this 2017 Guardian Science Book of the Year (following his similarly lauded The Disappearing Spoon, The Violinist's Thumb, and The Tale of the Dueling Neurosurgeons), Sam Kean tells the story of the air we breathe—which, it turns out, is also the story of Earth and our existence on it. Kean breezes through the periodic table, around the globe, and across time, revealing how the sextillions of molecules entering or leaving your lungs at this moment might well bear traces of Cleopatra's perfumes, German mustard gas, particles exhaled by dinosaurs or emitted by atomic bombs, or even remnants of stardust from the universe's creation.