Petri dish surface. Coloured atomic force micrograph (AFM) of the surface of a petri dish. Fibres of plastic can be seen. An atomic force microscope is used to study surfaces at an atomic level. An extremely fine spring-mounted probe is moved across the surface at a constant height. Any deflections are recorded and converted into a computer map of the surface. Magnification: x33,330 when printed at 10 centimetre wide.