The architecture of planetary systems evolves significantly with time, with several mechanisms acting on different timescales: migration within the native disk, expected to occur on few Myrs before disk dissipation; planet-planet dynamical instabilities, gravitational interactions, and circularisation of the orbit by tides from the host stars, which could be active on much longer timescales. Understanding the original configurations of the systems and the timescales on which these various

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... isms work is easier when observing planetary systems at young ages, with planets closer to their formation time and possibly also to their birth-sites. Transit space missions are significantly contributing in our view of young planetary systems at close separations, providing robust candidates to be followed-up with the radial velocity (RV) technique and to investigate their orbital and physical evolution. Indeed, these targets are also useful to validate models of planetary evolution as the result of the atmospheric photo-evaporation due to the high-energy irradiation of the young stellar host. Considering the crucial role played by previous space-based transit missions, PLATO is going to represent an unprecedented source of young planet candidates, allowing this field to enlarge the available sample and finally perform statistical investigations.