Light micrograph of Pyrocystis lunula marine dinoflagellate alga cells. The chloroplasts, the site of photosynthesis, are yellow. When present in large numbers Pyrocystis 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: x80 when printed at 10 centimetres wide.