Transmission electron micrograph of a mitochondrion inside a cell, showing the double outer membrane and numerous internal membranes (cristae, colored blue) where respiration takes place. Mitochondria provide cells with energy by oxidizing sugar and fat. They are found in almost all cells have their own DNA, and replicate autonomously. This cell is from digestive enzyme-secreting (acinar) tissue from a bat's pancreas. Magnification unknown.