  Stars are usually formed in clusters in the dense cores of molecular clouds.
These embedded clusters show a wide variety of morphologies from hierarchical
clusters with substructure to centrally condensed ones. Often they are
elongated and surrounded by a low-density stellar halo. The structure of an
embedded cluster, i.e. the spatial distribution of its members, seems to be
linked to the complex structure of the parental molecular cloud and holds
important clues about the formation mechanism and the initial conditions, as
well as about the subsequent evolution of the cluster.
