Mitochondria are the primary site of energy production for the cell and as such are essential for cell viability. These organelles are also involved in other processes including apoptosis and calcium homeostasis. Since mitochondria are not created de novo, they require the constant synthesis of mitochondrial- and nuclear-encoded proteins for their biogenesis. As mitochondria grow, they divide so that may be inherited by daughter cells following mitosis. Mitochondria also fuse in order to mix their contents. The dynamic nature of mitochondria is linked to metabolic and disease states, stress and quality control. Fission and fusion is co-ordinated by a group of dynamin family GTPases. Mitochondrial fission is executed by dynamin related protein 1 (Drp1) which is recruited to the outer membrane by adaptor proteins Mff and MiD49/51. Other players involved in fission include mitochondrial constriction machineries involving the ER and actin. More recently, the endocytic dynamin-2 has been implicated in the final scission of mitochondria. The precise molecular functions of these proteins, and their importance in mitochondrial fission, are being characterised.