The study of life and its existence in the universe, known as astrobiology, is now one of the hottest areas of both popular science and serious academic research, fusing biology, chemistry, astrophysics, and geology. In this masterful introduction, Lewis Dartnell tours its latest findings, and explores some of the most fascinating questions in science. What actually is 'life'? Could it emerge on other planets or moons? Could alien cells be based on silicon rather than carbon, or need ammonia instead of water? Introducing some of the most extreme lifeforms on Earth - those thriving in boiling acid or huddled around deep-sea volcanoes - Dartnell takes us on a tour of our solar system and beyond to reveal how deeply linked we are to our cosmic environment, and what we might hope to find out there.