The air around us is not just empty space; it is an integral part of the chemistry of life. Plants are made from carbon dioxide, nitrogen nourishes the soil and oxygen gives us the energy we need to keep our hearts pumping and our brains alive. But how did we come to understand what air is made of? How did we come to know that this invisible stuff around us contains anything at all? Gabrielle Walker tells the remarkable story of the quest to understand the air. It's a tale of heroes and underdogs, chance encounters and sheer blind luck that spans the entire history of science. It began as a simple desire to further our knowledge of the natural world, but it ended up uncovering raw materials that have shaped our modern world, unravelling the secrets of our own physiology and revealing why we are here at all.