TRIP steels exhibit superior mechanical properties; however, there is still a demand and possibility for further improvements. These improvements can only be realized after a thorough understanding of the relation between the microstructure and mechanical properties. The present work, therefore, aims at addressing the following research objectives:. First, obtaining an accurate and reliable description of the microstructure.. Second, correlating the high resolution microstructure description to the macroscopic mechanical properties, specifically to the high strain hardening rate and to the related martensitic transformation.. Third, identifying the effect of each microstructural parameter separately on the mechanical properties and find out the relative contribution of each parameter particularly on the martensitic transformation and the corresponding austenite stability.These objectives could provide a good insight for further improvement of the performance of TRIP steels, as well as for the optimization of the processing parameters.