  Multiple systems play an important role in the evolution of star clusters.
First we discuss several formation mechanisms which depend on the presence of
binaries, either primordial or of dynamical origin. Hierarchical configurations
are often stable over long times and yet may experience evolution of the
internal orbital parameters. We describe an attempt to model the eccentricity
change induced by the outer component using an averaging method, together with
the effects due to tidal dissipation and apsidal motion acting on the inner
binary. This treatment is adopted for systems with high induced eccentricity
which gives rise to some interesting outcomes of significant period shrinkage.
