These star-shaped grains of sand, collected from southern Japan, look like miniature works of art -- but they were not sculpted by an artist. They are the shells of microscopic organisms called foraminifera, which build intricate shells from the calcium carbonate they collect while drifting through the water. Their shells have settled on the seafloor for 500 million years, and are used by scientists to study the earth's changing climate. Learn more about the formation of sand and the animals that call it home in the Shores and Shallows exhibit at the Smithsonian's Sant Ocean Hall, and see more pictures of foraminifera shells.