The cycle of photosynthesis is the cycle of life, says science journalist Morton (Mapping Mars). Green leaves trap sunlight and use it to absorb carbon dioxide from the air and emit life-giving oxygen in its place. Indeed, plants likely created Earth’s life-friendly oxygen- and nitrogen-rich biosphere. In the first part, Morton, chief news and features editor of the leading science journal, Nature, traces scientists’ quest to understand how photosynthesis works at the molecular level. In part two, Morton addresses evidence of how plants may have kick-started the complex life cycle on Earth. The book’s final part considers photosynthesis in relation to global warming, for, he says, the Earth’s plant-based balance of carbon dioxide and oxygen is broken: in burning vast amounts of fossil fuels, we are emitting more carbon dioxide than the plants can absorb. But Morton also explores the possibility that our understanding of photosynthesis might be harnessed to regain that balance.