People who explore caves are called cavers or speleologists. (The study of caves is called speleology.) They go into caves for fun, exercise and to see the different formations. This can be a dangerous sport because caves sometimes have deep holes. Cavers also have to climb and crawl through the passages. Cavers usually go into caves with four or more people. Each person has 2 or 3 light sources. One light is attached to each helmet. People go into caves to try and explore more about the world.