Answer the following question given this paragraph: 

Friction occurs because no surface is perfectly smooth. Even surfaces that look smooth to the unaided eye make look rough or bumpy when viewed under a microscope. Look at the metal surfaces in the Figure below . The aluminum foil is so smooth that it’s shiny. However, when highly magnified, the surface of metal appears to be very bumpy. All those mountains and valleys catch and grab the mountains and valleys of any other surface that contacts the metal. This creates friction.


Q: The process of microscope mountains and valleys on the surface of a material interacting with another material is called?


A:
friction