Transcript: Star formation in molecular clouds occurs more slowly and less efficiently than the simple theory of gravitational collapse would predict. Regions of star formation do not only contain gas and dust however. They are threaded by weak magnetic fields. When the clouds begin to collapse the magnetic field lines are trapped and entrained and so the magnetic field increases as the cloud collapses. The gravity is opposed by magnetic pressure as the field lines are compressed and magnetic forces play an important role in any successful theory of star formation. Magnetic fields are also essential in explaining the bipolar outflows exhibited by young stellar objects.