Growth over the last century has improved economic well-being to an extent that our great-grandparents could not have imagined. But what causes economic growth, and how can it be assured? Harvard's Helpman here provides a systematic, relatively nontechnical, and closely reasoned review of two decades of academic research on these questions, some of it his own. He discusses the accumulation of physical and human capital, innovation, engagement with the world economy through trade and investment, and the legal and institutional underpinnings necessary for economic growth. He also addresses the impact of growth on poverty and income inequality. Here is a good place to learn what we know about the wellsprings of economic growth and what are the remaining mysteries.