What are foraminifera?
Foraminifera are single celled shelled marine protists. Informally, we call them 'forams'. They're ubiquitous in the ocean: they can be found from pole-to-pole and occupy both surface waters (planktic species) and ocean sediments (benthic species). Most are sand-grained sized, but some can be much larger, like large benthic species that live in lagoons and coral reef rubble.
Most forams build intricate shells (or 'tests') out of the mineral calcite (calcium carbonate). Some species build shells out of other materials in sediments (they're called agglutinated forams). The 3D models on this website are species that build their shells out of calcite.
Forams are abundant as fossils, and their fossil record extends back to the Cambrian (over 500 million years ago).
Why do we study forams?
Foraminifera provide information about past climate on Earth. Foraminifera 'assemblages', that is, the species of foraminifera present in a location, depends on the environmental conditions, such as the salinity and temperature of seawater. Fossil assemblages can be used to infer the environment the organisms occupied when they were alive. More importantly, when the foraminifera grow, elements in seawater (like magnesium and boron) are incorporated into their shells in trace quantities and the amount incorporated depends on the environmental conditions when the shells formed. The isotopic composition of the shell material also depends on environmental conditions. Scientists can analyze the composition of their shells and infer the environmental conditions that they grew in. Foram assemblages and their shell composition serve as 'proxies' for the environment when they grew.
Learn more about foraminifera here:
The Smithsonian has a slideshow on foraminifera.
Time Scavengers also has a great overview about foraminifera.