Light micrograph of the marine diatom Coscinodiscus spec. Coscinodiscus forms large cells consisting of two halves that are constructed like the lid and base of a box of chocolates. In this picture, the focus is on the centre of the cell with the nucleus. The brown chloroplasts are irregularly arranged at the edge of the cells. Culture material from the algae collection at the University of Cologne (CCAC). Microscopic contrast method : Differential interference contrast. Magnification 600x at a print width of 10 cm.