Polarised light micrograph of Haematococcus lacustris green algae. This is a freshwater, unicellular microalga with a complex lifecycle. The cells are normally green but under stress conditions, the cells change to larger globular cysts with an orange-red pigmentation. Haematococcus is a rich source of astaxanthin, one of the most powerful antioxidants in nature. Magnification: 93x when printed 10 centimetres wide.