Microbial sphere, coloured scanning electron micrograph (SEM). This is a symbiotic arrangement of several microscopic marine organisms found in the North Sea. At first, the sphere consists of bacteria and diatoms, then cyanobacteria (green filaments) grow in and on the sphere. The sphere falls apart after a few weeks. The spheres studied so far consist of Phormidium cyanobacteria, Navicula diatoms and heterotrophic bacteria. Magnification: x140 when printed 10cm wide.