After the primordial soup of hydrogen and helium atoms had formed, gravitation was the driving force of forming the structures in our Universe. While the Universe's large-scale web-like structure is well described by a collionsless plasma governed by gravitation, hydrodynamic pressure becomes a key opponent to the acting gravitational forces in forming smaller scale structures where the gas becomes denser and warmer. The collapse of small-scale gas fluctuations into stars and the formation and evolution of galaxies, however, is only made possible by the interplay with other physical processes, such as turbulence and radiative cooling. The chemical composition and temperature of the collapsing gas determines the masses of the stars forming and thus the blackbody radiation emitted form these. The radiation of these stellar populations as well as the explosions of the most massive stars are crucial processes in shaping the evolution of galaxies (and their observable light) as well as the intergalactic gas between them.
In my talk, I will provide an overview of the physical processes driving and shaping the formation of the large-scale structure, galaxies and stellar populations. I will also discuss approaches astronomers take to understand and constrain these processes from the light emitted by galaxies and the intergalactic gas detected by telescopes.