Cosmic background radiation: a hagiography

Full text. Cosmology advanced tremendously since Gamow and his students predicted the cosmic microwave background radiation, and since Penzias and Wilson observed it for the first time. The observations of the CMBR point to a Universe which is beautiful in its simplicity: the amazing richness of structures can be explained by a minimalistic set of well-known physical laws, a reasonable amount of free parameters, and 'natural' initial conditions which realize the idea of maximum entropy. We will revise the latest observations and show how the CMBR is presently allowing the study of the 'fine structure' of cosmological phenomena. We will also discuss the possibility of a detection of rotational modes (B-modes) in the polarization of the CMBR, that may reveal which processes (inflation ?) acted in the very early universe to endow it with these beautiful and simple properties. (author)