Microscopic, single-celled organisms called foraminifera have a fossil record that extends from today to more than 500 million years ago. Although each foram is just a single cell, they build complex shells around themselves from minerals in the seawater. These shells have accumulated in layers of sediment below the seafloor of the open ocean and in regions where the ocean once flooded the continents for millions of years. By examining the shell chemistry of these ancient forams, scientists can learn about Earth's climate long before humans ever walked the planet—and get insight into how climate changed in the past. Take a closer look at a few members of this fascinating life form.

In this photo of a shallow coral reef in the Pacific there are three species of forams. Their colors come from the symbiotic algae that live inside the foram shells.10 grains of star shaped sand collected from southern JapanColorful layers of a microscopic foram. Globotruncana falsostuarti -- a foram that lived about 75 million years ago, during the Cretaceous Period.Hedbergella sliteri - this specific specimen is the "holotype" for this species. That means it is the reference point for what all members of the species should look like.Hantkenina mexicana -- a foram with elongated shell chambers that lived between 45-49 million years ago, during the Eocene Epoch.Lenticulina secans-- this “benthic” foram lives on the seafloor. This specimen was collected from southeastern Tanzania.