Desmid and tardigrade. Polarised light micrograph of a Closterium sp. desmid (bottom) and a tardigrade (waterbear, top). Desmids are a common group of freshwater single-celled algae that have intricate cell walls. Waterbears are small, water-dwelling, segmented micro-animals with eight legs that live in damp habitats such as moss or lichen. They are classed as extremophiles as they can survive dry conditions by changing into a desiccated state, in which they can remain for many years. They have even been brought back alive after spending 10 days in the vacuum of space. Magnification: x200 when printed 10 centimetres wide.