Explore the intricacies of binary systems in this 47-minute conference talk by Ondrej Pejcha from Charles University, presented at the Kavli Institute for Theoretical Physics. Delve into the physics of circumbinary gas evolution and its influence on embedded binaries, from stellar systems to supermassive black holes in galactic nuclei. Examine observational signatures, numerical modeling techniques, and the similarities between massive black hole binaries and stellar binaries. Cover topics such as disc accretion, mass loss, radiation, and simulations, while gaining insights into the evolution of individual components and the background of these complex systems. Gain a comprehensive understanding of the current state of research and future directions in this field, as part of the "Building Bridges: Towards a Unified Picture of Stellar and Black Hole Binary Accretion and Evolution" conference.