So they use these extensions to wrap around specific regions of the axon and actually create those myelin. So let's move on to the fourth type known as microglia. So microglia are those cells that differentiate from monocides found inside the bone marrow. So inside the bone marrow we have monocides. They become microglia and then the microglia travels to the brain and they basically function as macrophages. And that means they basically engulf different harmful types of things such as some type of harmful debris.