1 Equilibrium and Non-Equilibrium States in NMR 2 Simple Relaxation Theory 3 Relaxation through Dipolar Interactions 4 The Redfield Relaxation Theory 5 Applications of Redfield Theory to Systems of Spin 1/2 Nuclei 6 Spectral Densities and Molecular Dynamics 7 NMR: The Toolbox 8 Measuring T 1 and T 2 Relaxation Rates 9 Cross-Relaxation Measurements 10 Cross-Correlation and Multiple-Quantum Relaxation Measurements 11 Relaxation and Molecular Dynamics 12 Applications of Relaxation-Related Measurements to Structure Determination 13 Relaxation and Chemical Exchange 14 Effects of Quadrupolar Nuclei 15 Nuclear Spin Relaxation in Paramagnetic Systems in Solution 16 Long-Lived Nuclear Spin States and Related Topics 17 Nuclear Spin-Relaxation in Other Aggregation States