In recent years, spurred in large part by the development of first-principles numerical simulations, the plasma astrophysics community has made important strides in understanding the plasma processes relevant for astrophysical systems. The next step, which will be a key topic of the MIAPbP program, is to connect the rich plasma behavior to observed radiative phenomena. These phenomena include old puzzles, e.g. hard X-ray emission from accreting black holes, gamma-ray flares from blazars, cosmic ray acceleration, giant magnetar flares and GRBs. Plasma physics is also key to solving new puzzles such as the cosmological FRBs and gamma-rays from neutron star mergers. The role of plasma instabilities is especially prominent in transient phenomena and strong connections are emerging between plasma physics and time-domain astronomy, a quickly developing observational field. Plasma physics also plays an increasing role in multi-messenger astronomy where main targets are energetic compact objects capable of producing neutrinos, gravitational waves, and nonthermal radiation. The current efforts to understand plasma behavior lay the foundations for the future of high-energy astrophysics. Within a two-week MIAPbP program, we want to facilitate progress in this direction by bringing together both senior researchers as well as early-career scientists.