Every second of every day, we are exposed to billions of neutrinos emitted by the Sun, and yet they seem to pass straight through us with no apparent effect at all. Tiny and weakly interacting this subatomic particle may be, but this book will show you just how crucial a role it has played in the evolution of the elements in the universe, and eventually, ourselves. We first start with an introduction to the basics of subatomic physics, including brief backgrounds on the discoveries that set the stage for major 20th century advances. The author, a distinguished theoretical physicist who has researched neutrinos for over thirty years, next explains in nontechnical language how and why the neutrino fits into the wider story of elementary particles. Finally, the reader will learn about the latest discoveries in the past half century of neutrino studies.  This semi-popular science book will appeal to any physics students or non-specialist physicists who wish to know more about the neutrino and its role in the evolution of our universe.