Coloured transmission electron micrograph (TEM) of archaea collected from an underwater thermal vent in the Pacific Ocean. Archaea are single-celled organisms that are similar to bacteria, but that also have characteristics of higher organisms. They are often found in extreme environments. This Archaean is a methanotroph, that is, it uses methane as an energy source. Magnification: x16,000 when printed at 12cm wide.