Abstract
Galaxies begin to glow when ordinary matter collapses into pre-existing dark matter halos, forming stars. Initially, the universal fraction of ordinary matter is 17 %, but due to feedback phenomena from star formation (supernovae, stellar winds), and also from active nuclei and black holes, ordinary matter is ejected, to represent only 4 % of the mass of galaxies. The fate of the various components of matter without the Universe will be followed as a function of time, through observations and simulations.
