Life is all around us, abundant and diverse. It is truly a marvel. But what does it actually mean to be alive, and how do we decide what is living and what is not? After a lifetime of studying life, Nobel Prize-winner Sir Paul Nurse, one of the world's leading scientists, has taken on the challenge of defining it. Written with great personality and charm, his accessible guide takes readers on a journey to discover biology's five great building blocks, demonstrates how biology has changed and is changing the world, and reveals where research is headed next. To survive all the challenges that face the human race today - population growth, pandemics, food shortages, climate change - it is vital that we first understand what life is. Never before has the question 'What is life?' been answered with such insight, clarity, and humanity, and never at a time more urgent than now. 'Paul Nurse is about as distinguished a scientist as there could be. He is also a great communicator. This book explains, in a way that is both clear and elegant, how the processes of life unfold, and does as much as science can to answer the question posed by the title. It's also profoundly important, at a time when the world is connected so closely that any new illness can sweep from nation to nation with immense speed, that all of us - including politicians - should be as well-informed as possible. This book provides the sort of clarity and understanding that could save many thousands of lives. I learned a great deal, and I enjoyed the process enormously.' -Sir Philip Pullman 'A nearly perfect guide to the wonder and complexity of existence.' -Bill Bryson 'Nurse provides a concise, lucid response to an age-old question. His writing is not just informed by long experience, but also wise, visionary, and personal. I read the book in one sitting, and felt exhilarated by the end, as though I'd run for miles - from the author's own garden into the interior of the cell, back in time to humankind's most distant ancestors, and through the laboratory of a dedicated scientist at work on what he most loves to do.' -Dava Sobel