In order to further enhance the great potential of the NEPS data and to open it up to external content, various add-on models are possible. On the one hand, there are explicit NEPS Call for Modules (CfM) at regular intervals to integrate additional content into the survey programme. On the other hand, qualitative or quantitative add-on studies can also be addressed by external parties to the participants of the start cohorts in the wide-meshed monitoring, if certain framework conditions are met.