Agroecology calls for a global approach, integrating scientific, practical, and advocacy dimensions, to redesign agricultural systems based on ecological and socio-cultural processes and emphasizing biodiversity. This review is grounded on the results of DIVERSIFOOD, a European H2020 multi-actor research project, and explores the concept of cultivated diversity using various dimensions relevant to foster sustainable organic food systems and agro-ecological transition. From the evaluation of underutilized genetic resources and forgotten crops, DIVERSIFOOD has proposed plant breeding strategies, on-farm experimentation, and statistical tools to create new populations, landraces, and organic cultivars with intra-varietal diversity. The added value of Community Seed Banks and forms of collective seed management in Europe have been described in terms of goals and activities, and their value for improving seed regulations, treaties, and genetic resources management is discussed. In the context of the current agro-food system characterized by standardization, DIVERSIFOOD raised awareness of qualities of ‘biodiverse food systems’ in which all actors have a role to play. It highlighted the critical capacity to preserve a diversity of cultural values embodied in ‘biodiverse products’, thereby involving consumers in collective strategies for reviving diversity,and empowering all actors of organic food systems to really and efficiently implement research within their farms and networks.