Kidney mitochondria. Transmission electron micrograph (TEM) of a section through a kidney tubule, showing numerous mitochondria (red). Mitochondria are a type of organelle found in the cytoplasm of eukaryotic cells that provide the cell with energy. They oxidase sugars and fats to produce chemical energy in the form of adenosine triphosphate (ATP). Therefore areas of high metabolic activity, such as the kidneys, contain high numbers of mitochondria as seen here. Magnification: x1,5000 when printed 10 centimetres wide.