Magnetic resonance imaging (MRI) has established itself as a major imaging modality in life science research and clinical practice. It is characterized by high spatial resolution, high soft tissue contrast, non-invasiveness, and universal applicability in terms of orientation and location of imaging areas. The procedure allows furthermore the investigation of physiological and pathophysiological processes, in particular in combination with magnetic resonance spectroscopy (MRS). MR methodology is not exhausted, new procedures and areas of application develop widely in life science and medicine. This article is limited to basic physical aspects.