Since the start of my Ph.D., I have the fortune to work on a diverse array of questions in theoretical astrophysics, related to the origins and the nature of dark matter, the formation and evolution of galaxies & supermassive black holes (SMBHs) as well as astrophysical fluid dynamics. These questions revolve on dramatically different physical scales in different epochs of the Universe, from the Big Bang 14 billion years ago down to the formation of our Milky Way galaxy and its satellites.