EOSC-Pillar gathers representatives of the fast-growing national initiatives for coordinating data infrastructures and services in Italy, France, Germany, Austria and Belgium to establish an agile and efficient federation model for open science services covering the full spectrum of European research communities. Our proposal aims to implement some of the main pieces of the EOSC jigsaw within a science-driven approach which is efficient, scalable and sustainable and that can be rolled out in other countries. National initiatives are the key of our strategy, for their capacity to attract and coordinate many elements of the complex EOSC ecosystem and for their sustainability, which will add resilience to the whole structure. We will combine these initiatives, who represent research communities in each country, with use cases of transnational networks working to implement FAIR data practices. Through the coordination of national initiatives, EOSC-Pillar will be able to support the gradual alignment of policy and practice among countries and compliance to EOSC standards. We are convinced that by federating national initiatives through common policies, FAIR services, shared standards, and technical choices, EOSC-Pillar will be a catalyst for science-driven transnational open data and open science services offered through the EOSC portal. These initiatives will emanate the promotion of FAIR data practices and services across scientific communities, sharing best practice, and igniting opportunities for interdisciplinary approaches in the EOSC. Above all, our vision is that national initiatives are key to involve user communities and research infrastructures both as test-beds for solutions, but also in their very design and sustainable evolution. For this reason, EOSC-Pillar’s workplan is built around selected user-driven pilots from 7 scientific domains, that will show EOSC in action and provide valuable input to guide the roll out of services for other communities.