This project explores the physics of extreme environments where strong magnetic fields interact with relativistic matter at very high temperatures and densities. Such conditions occur in the early Universe, within compact stellar objects like magnetars, and in quark-gluon plasma produced during high-energy nuclear collisions at relativistic colliders. Such systems exhibit unusual quantum behavior and offer critical insights into the fundamental forces of nature. The project seeks to deepen our understanding of how strong magnetic fields influence the behavior of matter under extreme conditions. This research aims at advancing scientific discovery in theoretical nuclear and astrophysics. Broader impacts include the training of undergraduate students and postdoctoral researchers. Outreach efforts will support project-based physics education at the university level and help develop a new generation of scientists equipped with advanced theoretical and computational skills. This work promotes the integration of research and education and contributes to building a strong scientific workforce. This research addresses fundamental questions in the theory of strongly magnetized relativistic systems. Using advanced quantum field theory techniques, the project investigates the influence of strong magnetic fields on the self-energy of fermions, the photon and gluon polarization tensors, and the vertex function in relativistic plasmas. While prior work has elucidated the absorptive part