Polarised light micrograph of Haematococcus lacustris green algae (orange) and a rotifer (yellow). 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. Rotifers, also called wheel animals, are common in freshwater environments. They use their cilia (microscopic hairs) and two toe-like projections for locomotion. They are surprisingly complex on the inside: they have a brain, reproductive organs, a bladder and a digestive system. Magnification: 93x when printed 10 centimetres wide.