At low supercooling the polymer crystallization is widely investigated by DSC. Extrapolation of this information to high supercooling (i.e. to conditions that are relevant during processing) is often doubtful because at high supercooling the morphology and the crystallization kinetics are fundamentally different. Since the cooling rate of conventional DSC instruments is not sufficient to reach high supercooling, i.e. structure formation at high supercooling cannot be investigated using such type of instruments . To overcome these limitations chip calorimeters with very high scanning rates have been developed. The Flash DSC 1 (Mettler-Toledo) allows scanning rates up to 40000 K/s. We demonstrate strategies to understand structure formation using fast scanning DSC. The measurements were performed on polyamides filled with nano-clay, polyolefines filled with carbon nanotubes or calcium carbonate and differently nucleated poly(ethylene terephthalates). Especially isothermal crystallization measurements after rapid cooling from the melt clearly show the influence of the fillers on the crystallization kinetics even at crystallization temperatures in the region of the maximum crystallization rate. In this type of experiments high cooling rates are crucial to prevent crystallization before the isothermal crystallization temperature. The morphology obtained during crystallization can be analyzed by subsequent DSC measurements at heating rates of several thousand Kelvins per second. These high heating rates are required to suppress reorganization.