Microfocus wide-angle X-ray scattering (WAXS) has been applied for analysis of the polymorphism of isotactic polypropylene and polyamide 6 prepared in a fast scanning chip calorimeter (FSC). Samples with a typical mass of few hundred nanograms, and lateral dimension and thickness of about 100 μm and 20 μm, respectively, were exposed to a defined thermal history in the FSC and subsequently analyzed regarding the X-ray structure at ambient temperature using an intense synchrotron microfocused X-ray beam. The relaxed melt of isotactic polypropylene was cooled at rates of 40 K s−1 and 200 K s−1 which allowed formation of α-crystals or mesophase, respectively. Polyamide 6 was isothermally crystallized at 95 °C and 180 °C which led to formation of γ-mesophase and α-crystals, respectively. This study demonstrated, for the first time, that FSC polymer crystallization experiments could be completed and expanded by subsequent in situ structure analysis by X-ray scattering.