In this work, the discussions, synergies and outcomes of the Outreach and Education session of the 39th International Cosmic Ray Conference (ICRC) are presented. The session brought together scientists, educators and public engagement enthusiasts from three complementary fields: astroparticle physics, multi-messenger astronomy and particle physics. An overview of worldwide initiatives in science communication and education in these fields is provided, emphasizing on the importance of long-lasting collaboration between the different communities. Furthermore, within the framework of the conference, an outreach event called STELLAR was held at CERN Science Gateway with contributions from participants of this session, and a brief description of this event is included.