TEM of a dividing mitochondrion in a cell of a human oncocytoma, a rare benign tumor of the human parotid salivary gland. The mitochondrion is divided into two by a membranous partition, and shows constriction at the level of partition. Continued ingrowth of the outer mitochondrial membrane into the partition will eventually result in the formation of two daughter mitochondria. Magnification @ 75,000x.