This book presents an elaborative account of information on nitroxide (aminoxyl) radicals, which have come to emerge as one of the most studied and developing topics of modern chemical physics. It has found critical uses in biophysics, molecular biology, polymer sciences and medical advancements. This book has been compiled with research works by experts renowned in the sphere of spin label/probe technique. The authors have presented an in-depth study of the latest trends and functions of nitroxide radicals. This book is an important source of academic literature for chemists, physical chemists, biophysicists, biologists, physicians and other masters in diverse disciplines. It will also be helpful in using nitroxide applications for promoting the progress in natural sciences.