Silks spun by arthropods exhibit a set of unique properties that have emerged as the result of over four hundred million years of evolution. Silks show the most optimized combination of tensile strength and deformation at breaking, yielding the highest work of fracture of any known material. These outstanding features have thrust an increasing interest in reproducing or even improving the properties of natural silks. However, the advances in the field are hampered by an incomplete knowledge on the relation between microstructure and mechanical properties as well as by uncertainties related to the influence of processing in the performance of the fiber. In this work we present some of the most significant contributions of our groups to the field, stressing the possibility of controlling the tensile properties of silks and the contribution of this basic knowledge to the production of artificial regenerated fibers. Spider silk shows a large variability that it is thought to allow the spider to adapt the fibers to its immediate requirements, but represents a major drawback for its study or application. The development of the wet stretching process has allowed the modification of silk fibers in a controlled and reproducible way for the first time. Besides, recent improvements in the spinning of regenerated silkworm silk fibers have led to artificial fibers with properties that approach those of natural silks. These progresses allow envisaging the production of bioinspired fibers in a not too distant future.