Algebraic varieties are shapes defined by polynomial equations. Smooth Fano threefolds are a fundamental subclass that can be thought of as higher-dimensional generalizations of ordinary spheres. They belong to 105 irreducible deformation families. This book determines whether the general element of each family admits a K hler-Einstein metric (and for many families, for all elements), addressing a question going back to Calabi 70 years ago. The book's...