Foraminifera are testate protozoans that exhibit a bewildering variety of test composition and morphology (Figure 1). They inhabit all marine environments from the intertidal zone to the deep ocean floor, they range from the poles to the tropics, and they can be planktonic or benthonic. Their abundance in sediment samples may reach tens of thousands per square meter and their diversity in tropical environments may exceed 60 or 70 species in a sample of 300 individuals. A geological range stretching from the very earliest Cambrian through to the present day is characterized by varying patterns of evolution and extinction that have proven to be of considerable biological and geological significance.