Coloured scanning electron micrograph (SEM) of Favocassidulina favus, a foraminiferan microfossil. Foraminifera are marine, single-celled protozoa that construct and inhabit a calcium carbonate shell composed of several chambers. These are usually penetrated by pores through which the cellular content is extruded to catch their prey. Magnification: x160 when printed at 15 centimetres wide.