|Title||Formation of Star Clusters|
Star clusters form in the densest part of a hierarchy of structures in the interstellar medium. Unbound stars continue the hierarchy to larger scales in OB associations and star complexes, while the clusters themselves contain smaller sub-clusters when they are very young, before the bound stars mix up. The conditions for cluster formation are present in the gas even before the stars form, including the high mass fraction of dense cores that is necessary for cluster boundedness when the less-dense gas eventually leaves. The initial stellar mass function and the cluster mass function seem to have similar origins, both coming from cloud structure. This talk will review the processes of star formation, cluster formation, and the IMF that are observed to operate over a wide range of scales.