Abstract: Cosmic rays interact with astrophysical systems across a vast range of scales, from turbulent galactic environments to the large-scale structure of the Universe. Closely linked to violent, high-energy processes, they act as a dynamic feedback agent, regulating the physical conditions and long-term evolution of galactic and circum-galactic ecosystems. Depending on their energy, cosmic rays can also escape from their host galaxies, propagate through the cosmic web, and produce multi-wavelength and multi-messenger signatures that encode information about their interactions, environments, and transport physics. In this talk, I will highlight key observational tracers, including those from multi-messenger probes, that can be used to map the physical effects of cosmic rays across astrophysical environments and extend studies of galaxies beyond traditional astronomical techniques. I will also examine the role of cosmic rays in shaping baryonic flows around galaxies, and discuss their fate as they traverse the magnetized large-scale structures of the Universe, including the highest-energy particles that may never reach us on Earth.