Coloured scanning electron micrograph (SEM) of the shell of an Elphidium crispum, a formaniferan microfossil. Foraminifera are marine single-celled marine 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: x180 when printed at 15 centimetres wide.