"Stronger and more ductile steels are increasingly demanded for advanced applications. Latest investigations show that nanostructured steels formed by non-equilibrium phases increasing strength, such as martensite and bainite, and enhancing strain hardening, such as austenite, fulfil these demands with outstanding performance.In the last few years, I have observed that non-equilibrium phases strongly affect each other’s formation and stability, with effects on the kinetics of the microstructure development. Thus, I theoretically and experimentally proved that carbon enrichment of austenite, essential for its stability at room temperature, occurs at a high rate via diffusion from martensite. Moreover, I showed that martensite triggers bainite formation, which significantly increases bainite kinetics. I believe that these interactions between non-equilibrium phases constitute a revolutionary tool for the development of nanostructured steels in the future.This project addresses a new concept to create novel nanostructured steels in which the microstructure development is controlled by interactions between non-equilibrium phases. This innovative idea opens an unprecedented approach for the design of metallic alloys. Since interactions between phases affect each other’s formation and stability, the project focus on the fundamental study of nucleation and growth of non-equilibrium phases as well as on the analysis of interactions. Investigations will combine the integrated application of advanced experimental techniques with atomic and micro scale analysis of structures by simulations. The project continues with the local analysis of the effect of non-equilibrium phases on the mechanical properties of the steels. The identification and explanations of mechanisms will allow the creation of new nanostructured steels based on non-equilibrium phases’ interactions."