So you already know what wet felting is and look for further details on nuno felting? It is a very young technique discovered in 1992. It involves bonding loose fibers with sheer fabric. Japanese word ‘nuno’ means cloth.
With this basic knowledge you can try to imagine a colander and pasta. When you hold the colander still, only a small amount of pasta passes through its holes. Shaking the colander you can only increase the mess. In nuno felting technique wool fibers are your pasta. Silk, linen or other fabric with its open weave is your colander. Mess in this case is actually something you are aiming for.
Remember rubbing wool during wet felting process? Nuno felting is pretty much the same. It is all about pushing wool fibers through the fabric and making links between these two materials stronger and stronger.