Open Science is the emerging paradigm for future scientific activities. The given proposal (HORIZON-MSCA-DN-2021) sees data sharing (DS) as one of the central activities in performing open science. Data sharing is essential for the reproducibility of scientific results. Furthermore, it is the starting point to explore the robustness of results towards methodological or sampling variability (different data sets, processing of data, statistical strategies for analysis, representing and interpreting results). A meta-analysis on independent patient data is a typical activity towards this goal. For a planned project, DS can replace pilot studies and provide valuable information in a cost- and time-efficient way. DS allows to use independent data for the validation of own findings and to strengthen claims based on new hypotheses. DS also provides an efficient basis for new research. It can replace expensive studies and provides a useful data base to develop new concepts. The proposal proposes an approach to enable students to perform data sharing on a high level of professionalism. Students need to gain the competencies to provide high quality data for DS as well as to be able to use DS for their own research. The proposed MSCA-ETN teaches and trains these competencies, it also implements research on aspects of DS as well as research projects which need DS to be performed. It explores good practice for DS as well as its relevance. It also discusses DS from its legal, societal, and philosophical point of view as well as state of the art on patients’ perception of DS. The MSCA-ETN concentrates on the sharing of clinical trials data. Data from clinical trials are a rich source of clinical information, highly structured and clearly explained by the accompanying protocols. There are less measurement errors as well as more well-defined content compared to medical real world data. At the same time data from clinical trials cover relevant innovations in a wide spectrum of medical fields. It is interesting to explore if the sum of clinical trial data may even cover more aspects of interest for medical research as by real world clinical data. Clinical trials data is provided by the patients recruited into the specific trials. Therefore, it is also relevant that data sharing is understood and accepted within patients. What are best practices to inform about and engage trial participants in clinical trial data sharing? DS from a legal, societal, and philosophical point of view as well as state of the art on patients’ perception of DS.