Mitochondria are essential and dynamic cellular organelles differing in size, subcellular distribution, and internal structure. These aspects of mitochondrial morphology are intimately controlled by a growing number of mitochondrial morphology shaping proteins. The past decade has revealed remarkable and often unexpected new insights into the molecular regulation and physiological impact of mitochondrial morphology maintenance. Obviously, proper mitochondrial dynamics, resulting from a tightly regulated equilibrium between opposing mitochondrial fusion and fission activities, is a prerequisite for normal organelle function. Consequently, a disturbance of these activities results in mitochondrial dysfunction and, thus, can lay the foundation for human disorders. Here we specifically focus on recent advances in our understanding of the regulation, activity, and function of dynamin-related protein 1, the main factor for controlled mitochondrial fission.