Wet felting has been known for thousands of years ... probably 'discovered' accidentally by someone with good observation skills.
This sample was made by layering combed fleece in alternate directions, adding hot water and liquid soap. We then 'smooshed' the bag with our fingers until it reached the 'prefelt' stage. The little balls are made with a single felting needle with little barbs.
This sample was made with my friend Rose. Wool was felted through a more involved process. The result is a semi-sheer felt that is as light as a feather.
The second photo shows the felt held up with the sun behind - to show the sheerness. My fingers show as shadows.
The last example is an ATC made with an embellisher, a machine that has several felting needles. It doesn't use thread or bobbin. The felt / threads are held in place by the barbed needles embedding the decoration in the background fabric.