In the present study, the structural and morphological development during melt spinning of polyethylene and poly(vinylidene fluoride) fibers was studied using simultaneous in-situ synchrotron small- and wide-angle X-ray scattering (SWAXS) techniques. The spinning apparatus consisted of a single screw extruder, which was mounted on a horizontal platform that could be translated in the vertical direction allowing different spinneret distances to be sampled with the X-ray beam. Effects of take-up speed (10.6-61.0 mpm) and spinneret distance (30-87.5 cm) on crystallinity and morphological parameters were investigated. A suggested model of structural development during crystallization details the formation of defective shish crystals, followed by the formation of kebob crystals. The defective shish-kebob structure eventually transforms into a well-defined lamellar structure. This model is consistent with the qualitative appearance of the two-dimensional SAXS and WAXS patterns, as well as the quantitative analysis of the SAXS/WAXS data using position-sensitive wire detectors.