Abstract 

   Most stars in the Galaxy are found in clusters. How molecular clouds collapse and fragment to give rise to a cluster of stars has been one of the central questions in star formation for decades. The Jeans mass, the characteristic mass of fragments, is ~ 1Msun for typical physical conditions in (pre)cluster forming clouds. This value ties to the stellar mass at the peak of the Initial Mass Function (IMF), and may explain the formation of most stars in a cluster. Massive stars, on the other hand, contain masses at least one order of magnitude greater than the Jeans mass. Therefore, their formation poses a challenge to our current understanding in star formation.
   Both micro-turbulence and magnetic fields can suppress fragmentation and increase the equivalent Jeans mass in clouds to facilitate massive star formation. In this talk, I will review recent progress in probing magnetic fields in molecular clouds, and its effect on the fragmentation and the formation of massive cores. I will also discuss star formation in the Galactic Center environment where dense clouds are massive enough to form massive star clusters, but there appears to be a lack of present star formation. I will present results from recent search for deeply embedded protostars in the Galactic Center clouds.