Radiolarians are marine microorganisms composed of siliceous skeletons. These tiny creatures play a crucial role in understanding the geological history of the Earth. They have many synonyms such as radiolaria, radiolarium, radiolarite, and radiolarian ooze. Radiolaria is derived from the Greek words "radius" meaning ray, and "laros" meaning "catcher." Radiolarian ooze refers to the sediment that accumulates on the ocean floor, primarily composed of radiolarian shells. Radiolarite is a type of sedimentary rock composed mainly of radiolarian remains. The study of radiolaria requires specialized equipment and techniques and is fundamental to the accurate determination of the age and formation of rocks and sediments.