While Europe looking for innovative strategies and means to foster an increase in skilled personnel in STEM, secondary education institutions are holding a key to unlock STEM potential. This calls for a joint action on national and international level in order to contribute to resolution of European level challenges by targeting teachers from STEM focused schools, who are the leaders, the vehicles of change and multipliers in STEM education in their countries, working with future generations and prospective employees in STEM fields. Project “STEM capacity building” aims to build a critical mass of teachers capable to implement a cohesive approach in STEM (science, technology, engineering and mathematics) teaching, which is based on ideas of values promotion, more complex integration in STEM education and learner-focused approach, and contribute to the development of responsible individual, who uses science to contribute to the progress and well-being of society.The project brings together partners with experience in STEM education and teacher professional development. During the lifetime of the project (35 month) partners from Greece, Lithuania, Netherlands, Portugal and Spain will identify new and explore effective forms and methods in STEM teaching, learning and assessment; share experience of good practice in STEM education; develop teachers’ skills and competences necessary for cohesive STEM education implementation; support the development of international network of STEM teachers and peer learning community.Project partners will develop STEM focused MOOC (umber of modules on MOOC – at least 8), Long-Term Professional Development (in-service training) program for teachers and educators (40 h. 2-4 modules) and Collection of Good Practices (no less than 10 by partner) to be used for dissemination in national and regional PD Centres, Teachers of STEM Subject Associations (or other forms of STEM teacher unions). To reach those goals 5 short-time joint staff events (total 72 participants), 4 transnational partnership meetings (total 60 participants), 5 national dissemination events (total 250 participants) and 1 international Roundtable discussion (25 local and 15 foreign participants) will be organised.Number of teachers, educators and students indirectly involved in project – 3592 (each partner involves 10-15 schools, at least 30 teachers and educators, 500 pupils’, total 3180 participants.These activities will be carried out on a basis of through mutual planning, based on partner cooperation, transparency and eligibility using distant and face-to-face communication means. The outputs will be developed with an aim to reach a wide teacher audience, which will be ensured through output translation to local languages. It is expected that Project will contribute to improved basic, didactic and subject competences of STEM teachers. Partners believe that Outputs intellectual base and experience from Output activities will enhance innovative learning in the classroom. Teachers will change their attitudes and will become open to discuss and share STEM pedagogy experiences with international peers. In the long term the Project expects STEM education know-how multiplication to other schools/teachers and involvement of other schools in Output exploitation. Partners expect that Project results and cooperation for STEM education advancement will build a support on STEM PD initiatives among PD centres and policy makers and current cooperation in the Project will build fundamentals for future cooperation in STEM PD.