Felt

One of the oldest forms of textile art, felting involves matting, condensing, and pressing woolen fibers together. While store-bought sheets of felt fabric are made using hot water, needle felting mimics the same process but is instead carried out using a felting needle. The technique involves moving the felt fibers back and forth using the many sharp barbs on the needle, pulling the fibers in and locking them into place.
-My Modern Met