Cosmonauts are astronauts from Russia or the former Soviet Union who are trained to travel into space. They undergo rigorous training in various fields, including science, engineering, and physical fitness, to prepare for missions aboard spacecraft like the Soyuz and the International Space Station (ISS). The term "cosmonaut" comes from the Greek word "kosmos," meaning "universe." Cosmonauts conduct experiments, perform spacewalks, and contribute to international space research. Their work helps advance our understanding of space and supports future exploration efforts.