In the last few years, functional magnetic resonance imaging (fMRI) has become the preferred technique for brain mapping because of its superior spatial and temporal resolution. Other factors that have contributed to the popularity of this imaging method are the increasing availability of scanners and the technological advances made in data acquisition and analysis. This paper describes basic principles of fMRI essential to a comprehension of the capabilities of this complex technology. In particular, it focuses on blood oxygenation level dependent (BOLD) contrast, on the experimental procedures, as well as on possible imaging techniques and statistical analyses. Examples for studying brain-behavior-relationships come from research in the context of emotion in healthy subjects as well as in emotional dysfunctions in psychiatric patients.