Spectroscopic methods are not only important as an analytical tool, they also provide information about fundamental physical and chemical properties of molecules, the molecular and electronic structure, and the dynamic behaviour of molecules. Starting from a comprehensive quantum mechanical description, ESR Spectroscopy in Membrane Biophysics introduces the optical (IR, Raman, UV/Vis, CD, fluorescence and laser spectroscopy) and magnetic resonance (1D and 2D—NMR, ESR) techniques. ESR Spectroscopy in Membrane Biophysics is a timely review of the increasing interest in using spin—label ESR as an alternative structural technique for NMR or X—ray diffraction. It is aimed at training an audience to learn ESR spectroscopy to determine membrane protein structures, conformational dynamics and protein—lipid interaction.