Traditionally, the materials studied by physicists have uniform properties and can readily be classified as solids, liquids, or gases. However, many materials of great interest for technology, chemistry, or biology, have complex structures and properties that vary from point to point and time to time. Among these are such materials as liquid crystals, polymer solutions or melts, colloids, foams, and gels, which have come collectively to be called "soft matter." They generally consist of organic molecules that interact weakly, so that individual phases are stable only over small temperature ranges.This text, intended for students with some knowledge of quantum mechanics, discusses the physics of these materials. It begins with discussions of the chemical bond and the interactions that bind molecules into condensed matter, of the ordering (crystalline or otherwise) one finds in condensed matter, noting that for soft matter the order is intermediate between that of crystals and that of typical disordered fluids. The discussion then turns to phase transitions, elasticity, and dynamics, using liquid crystals as the focus. A discussion of growth phenomena and fractals introduces a detailed treatment of dislocations and defects that clarifies many concepts by using insights only recently developed from the study of liquid crystals. The book concludes with discussions of surface phenomena, the stability of colloidal systems, and structural properties of polymers. The detailed exposition, the emphasis on physical principles, and the exercises at the ends of each chapter will make this a valuable introduction to this rapidly growing area of research.