In recent years, there has been a focus on promoting the uptake of STEM subjects in schools. This has been driven by the need to ensure that young people gain the knowledge and skills essential to help them participate in a society in which mathematics, science and technology are increasingly important. Nevertheless, reform efforts, including curriculum development, have treated the STEM subjects mostly in isolation. Recognizing that efforts for education within each individual STEM discipline would encourage a wide range of conservations about different important aspects of teaching and learning, this conference considered the potential benefits and challenges for the integration of various STEM's characteristics into education. In order to prepare students to address the problems of our society, it is necessary to provide them with opportunities to understand these problems through rich, engaging and powerful experiences that integrate the disciplines of STEM. This volume contains selected papers presented at the Hellenic Conferences "Innovating STEM education -HiSTEM 2016 and 2018" organized by the Postgraduate Program "Interdisciplinary Approach on Science, Technology, Engineering and Mathematics in Education -STEM Education" (stemeducation.upatras.gr). The first eleven papers were presented at the HiSTEM 2016 Conference and the last six papers at the HiSTEM 2018 Conference. These papers were selected after a peer review process from the conferences' submitted papers. The conferences provided a platform for dissemination of best practices in teaching and learning STEM in Greece and also inspired and empowered STEM educators to improve teaching quality, to increase engagement in STEM education and career pathways, to connect students with real life industry relevancy and to drive creativity, inquiry-based learning, problem-solving and project-based learning.