Crystallization during microinjection molding is investigated relative to process conditions. Modulus and hardness of the skin layer are higher than the core layer, regardless of core structure. Young's modulus, strain at break and yield stress all increase with an increase of skin ratio. The relationship between process, morphology and mechanical properties is studied for micro products. By using in-line process monitoring, flow induced crystallization is characterized by shear stress and apparent specific work. Shear stress is shown to be a good candidate to characterize the formation of highly oriented structures under actual microinjection molding processes. This may provide a method for in-line control of morphology development, and then final properties, by controlling the flow conditions.