This book describes the main methods of one- and two-dimensional high-resolution nuclear magnetic resonance spectroscopy in liquids within the quantum-mechanical formalism of the density matrix. In view of the increasing importance of NMR in chemistry and biochemistry, the work is particularly addressed to those scientists who do not have a working knowledge of quantum calculations. This knowledge is provided in the first part of the book through a description of quantum mechanics as applied to spin systems. This section is self-contained and limited to essentials. A final chapter is devoted to the principles of relaxation theory. By providing readers with practice in the theoretical tools of NMR, this book opens the way for a critical analysis of comprehensive treatises or articles on new methods. The emphasis throughout is on the actual use of NMR, so the text is neither oversimplified nor overly theoretical. The aim is to describe the basic theoretical tools needed to understand and fully exploit the valuable potential of high-resolution NMR.