Present work describes an ultra-fast scanning calorimeter that is capable of controlled cooling and heating at rates up to 100 000 K/s as well as isothermal measurements with time resolution of 0.1 ms. The technique was applied to study crystallization kinetics of polymers and monodisperse n-alkanes. It is shown that the bend in the isothermal crystallization kinetics curve of n-alkanes is not the
transition between formations of structures with different folding indexes, but it is rather caused by the interplay of different processes with different kinetics as well as a self-poisoning effect.