Transmission Electron Micrograph (TEM) section of a single mitochondria (pink) in the phytoflagellate Euglena, showing the 2-membraned envelope and granular stroma; the inner membrane is infolded into cristae which increase the surface area available for the location of F1 particles carrying enzymes concerned with the oxidative processes of respiration; in the euglenoids the flattened cristae are characteristically constricted at the base; the stroma contains small ribosomes and other respiratory enzymes mitochondria are found in the cell wherever an energy-needing process is occurring; outside of the mitochondrion, the cytoplasm contains large ribosomes and portions of a lysosome and a chloroplast. Magnification: 30,000x.