Natural fibrous biopolymers like proteinaceous silk or collagen fibers are sophisticated hierarchically structured materials, combining a set of interesting features, e.g. extraordinary mechanical properties, biocompatibility, and ease of functional modification. We focus on spider silk as well as collagen biopolymers, and utilize a well-established biotechnological approach to produce various recombinant protein proteins [1, 2]. By using self-assembly as well as various processing technologies like wet-spinning, electro-spinning, and microfluidics, we have been able to produce high-performance fibers with various diameters from nano- to micrometers. In addition, the fiber properties have been customized upon varying the molecular design of the underlying proteins, as well as by functional modifications. The green biopolymer fibers show impressive mechanical properties in par or even better than the natural blueprint, and many man-made fibers . Moreover, the various protein fibers exhibit high biocompatibility and, in the case of collagen microfibers, provide a good template for neuronal cell alignment and axon growth along the microfiber axes . Thus, green biopolymer fibers have a great potential for medical applications and tissue engineering including peripheral nerve repair, but also for technical ones, such as innovative filter systems.