Relativistic cosmic-rays created by stellar and black hole feedback may play an important role in many aspects of structure formation. Cosmic-rays can drive outflows from star forming galaxies and heat diffuse gas in the circumgalactic and intergalactic medium.  In this talk I will describe some of the possible impacts of cosmic-rays on galaxy formation, observational probes of their impact, and the theoretical uncertainities in our understanding of the role of cosmic rays in structure formation.