Light micrograph (fluorescent microscopy) of a Micrasterias sp. desmid green algae. Desmids are a common group of freshwater single-celled algae that have intricate cell walls. Micrasterias are highly adapted to nutrient-poor, acidic water. The ultraviolet light used to illuminate the specimen causes the chlorophyll to autofluoresce in red. The specimen was dyed with a fluorescent dye to highlight the rim of the alga. Magnification: x300 when printed at 10 centimetres wide at its longest edge.