The Cosmic Origins Spectrograph (COS) is revealing a surprisingly complex and dynamic circumgalactic media surrounding the range of galaxies spanning Hubble tuning fork. I simulate galaxies and their galactic halos using cosmological hydrodynamical simulations. My students, collaborators, and I relate the gaseous signatures observed by COS to the dynamical processes of gas accretion, outflows, and hot halo formation that regulate galaxy growth and evolution. The thousands of orbits of COS UV spectroscopic data focused on the circumgalactic medium uniquely probe the history of gas originating from the intergalactic cosmic web on its journey to the galactic sites of star formation. I am specifically interested in how star formation is quenched in passive "red-and-dead" galaxies, the role of supermassive black holes in feeding back upon gaseous halos, and simply figuring how much stuff is around galaxies of all types. I run and analyze EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulations, and do not limit myself to wavelength (from the radio to the X-ray), redshift (the present-day Universe to the Epoch of Reionization), or environment (field galaxies to massive clusters).