Coloured scanning electron micrograph (SEM) of a fossilised Stephanopyxis sp. diatom( aka Eupyxidicula grunowii). The characteristic feature of diatoms is their intricately patterned, glass-like cell wall, or frustule. The frustule often has rows of tiny holes, known as striae. Diatoms are among the most diverse species on Earth, with the number of diatom species ranging from 10,000 to 200,000. Scientists are discovering new species every year. Magnification: x2650 when printed 10 centimetres wide.