Magnetic resonance imaging (MRI) is, arguably, the most complex modality utilized in modern radiology. Signal generation is an interplay of classical and quantum physics that relies on magnetic moments, electrical and magnetic fields, and induction. This chapter reviews the basic underlying physics and technology that is necessary for image formation with a focus on a basic and intuitive understanding of the process. Practical implementation of MRI in the clinic is dependent on the optimization of image quality. MR acquisitions have more than twice the number of user-selectable parameters compared to other modalities. Further, each of these parameters typically impacts multiple facets of image quality and safety. This chapter discusses user-controlled acquisition parameters with a focus on their impact on image quality and tradeoffs that must be considered. Finally, although the dangers of MRI have been apparent for decades, it is only in the past decade that a formal safety structure has taken form and begun to be implemented widely in clinical practice. This chapter reviews the dangers of MR scanning, discusses methods to mitigate risks, and lists regulatory limits that are important in clinical MR practice.