Published online by Cambridge University Press: 16 November 2011
In this lecture, the general properties of molecular clouds are presented, then the physics of the earliest stages of star formation is introduced thanks to a simplified stability analysis of these clouds. We later compare the outcomes of this analysis with observations of molecular clouds and point out the complex interplay of gravity, magnetic fields and turbulence necessary for the understanding of star formation processes, with a special emphasis on preliminary results from the recent Herschel Gould Belt survey.