Mitochondria are subcellular organelles that coordinate numerous metabolic reactions, including those of the respiratory complexes that produce the ATP that powers cellular reactions. They have often been depicted as static, with a kidney-bean shape, but there is a growing appreciation of their dynamic nature. Moreover, they are strikingly varied in structure, ranging from small, spherical particles to long, interconnected filaments. Mitochondria are also highly motile and constantly move in a directed manner along cytoskeletal tracks within cells.