In our quest to elucidate the origin of the universe and the formation of galaxies, particularly that of the Milky Way in which we live, astounding progress has been made in recent years through observational and theoretical studies. Not only have gigantic surveys covering a large fraction of the sky brought statistics enlightening evolutionary paths of galaxies, but powerful instruments, such as radio interferometers and ground- and space-based op- cal/infrared telescopes, have been able to map individual objects with high sensitivity and spatial resolution. Yet we do not fully understand...

Modern astronomy has stretched its domains of exploration tremendously. Not only objects at very large distances and very old states of the Universe can be examined, but also all kinds of radiations and phenomena are now accessible. Astronomers constantly move from considerations about very - luted to very dense systems. Hot and energetic systems, being the easiest to observe, have attracted a lot of attention. However the cold and low energetic states have been so- what neglected, either because being harder to observe they appear unexc- ing, or because being less well known they tend to be...

In our quest to elucidate the origin of the universe and the formation of galaxies, particularly that of the Milky Way in which we live, astounding progress has been made in recent years through observational and theoretical studies. Not only have gigantic surveys covering a large fraction of the sky brought statistics enlightening evolutionary paths of galaxies, but powerful instruments, such as radio interferometers and ground- and space-based op- cal/infrared telescopes, have been able to map individual objects with high sensitivity and spatial resolution. Yet we do not fully understand...

Our knowledge of the Milky Way has been deeply renewed since a dozen years, following the results of the astrometric satellite HIPPARCOS, and those of large stellar surveys. Many concepts thought to be well established disappeared, to be replaced by others going towards a larger complexity: in particular, the discovery of radial migrations of stars has blurred the simple image that we had of the Galactic disk. There has been large progress in some domains, for instance the physics of the Galactic Center with its super-massive black hole; other problems remain unsolved, such as the nature of...