Nanobacteria. Coloured scanning electron micro- graph (SEM) of nanobacteria (or nanobes, grey) on sandstone. These are thought to be the smallest self-replicating organisms, 20 to 150 nanometres in size, smaller than other bacteria. They were found in 200 million year old sandstones taken from 3-5 kilometres below the seabed. When the rocks were opened, the nanobes multiplied and grew in the laboratory. Tests show they contain DNA (deoxyribonucleic acid), the molecule containing the instructions for life. They were discovered by Philippa Uwins at the University of Queensland, Australia. Magnification: x5000 at 6x7cm size.