Light micrograph of Pyrocystis lunula (Gr.pyro, fire & Gr. kystis, bladder) marine dinoflagellate alga cells, showing a spindle shaped older cell and a rounded younger cell. The chloroplasts glow in yellow color under Darkfield illumination. Pyrocystis in mass reproduction causes a bright bioluminescent ocean glow at night. Culture material of the Culture Collection of Algae at the University of Cologne. Microscopic contrast method: Darkfield contrast. Magnification 180x when printed at 10 centimetres width.