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   61029
   Recent molecular and NIR observations of relatively large regions of
   sky revealed that the dense and massive clusters are the units of star
   formation in a giant molecular cloud, which is usually associated with
   OB association. They appear to be birthplace of most OB stars, and the
   cluster-mode star formation is the dominat mechanism to form most stars
   in OB associations. We proposed the hard X-ray observations of the
   embedded population of PMS stars and protostars in the NGC 2264. NGC
   2264 is the young ( < 5 Myr ) and rich cluster in the Mon OB1
   association. Comparison with X-ray emission from low mass star forming
   region will provide new insights into the embedded cluster formation
   and stellar birth in a giant molecular cloud.
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