Understanding how collisionless plasmas convert the energy of turbulent flows and electromagnetic fields into energetic particles is a central challenge in space and astrophysical plasma physics. These processes govern phenomena ranging from magnetic reconnection in the near-Earth space environment to the origin and evolution of magnetic fields in galaxies and galaxy clusters. Despite their importance, they remain poorly understood because they involve a complex interplay between macroscopic plasma dynamics and kinetic processes occurring over a wide range of spatial and temporal scales. This project addresses three closely connected problems: particle energization during magnetic reconnection, the kinetic origin and amplification of astrophysical magnetic fields, and plasma instabilities responsible for particle heating and injection at collisionless shocks. We combine fully kinetic particle-in-cell simulations, Eulerian Vlasov-Maxwell simulations, and advanced collisionless fluid modelling to investigate these processes across complementary physical regimes. The project builds directly on the results of our previous NAISS allocation, which resulted in multiple peer-reviewed publications and demonstrated the capability of these simulation approaches to address previously inaccessible plasma regimes. The required simulations span several orders of magnitude in scale and require both large three-dimensional computations and high-dimensional phase-space resolution. We therefore request continued CPU resources for particle-in-cell and advanced fluid simulations, together with GPU resources for the Gkeyll Vlasov-Maxwell solver, enabling substantially higher phase-space resolution than previously feasible. These calculations will provide the computational foundation for ongoing projects funded by the Knut and Alice Wallenberg Foundation and the Swedish Research Council.