The EU Horizon 2020 project, Mainstreaming Ecological Restoration of freshwater-related ecosystems in a Landscape context: INnovation, upscaling and transformation (MERLIN) includes the aim to develop transformation strategies to mainstream Nature-based Solutions (NbS) to restore freshwater ecosystems. To achieve this the project is working with (public policy and market orientated) actors from different sectors, including Water Supply, Hydropower, Navigation, Peat Extraction, Agriculture and Insurance. This will enable MERLIN to contribute to achieving the EU Green Deal objectives (climate resilience, improved biodiversity, zero pollution, sustainable food systems, health and wellbeing). Although it is contended that transformation to mainstream NbS will emerge through multiple actions by the state, market and citizens, there is a lack of clarity about the meaning of transformation and how it occurs. In particular, the literature has framed the transformation process quite differently. This (working) document aims to foster a common understanding of transformation and develop a comprehensive framework for understanding and guiding transformative change processes.