  Observations have revealed that most stars are born in clusters. These
systems, containing from tens to thousands of stars and typically significant
mass in gas in the youngest systems, evolve due to a combination of stellar and
star-gas interactions. Simulations of pure stellar systems are used to
investigate possible initial configurations including ellipticity, substructure
and mass segregation. Simulations of gas-rich clusters investigate the effects
of accretion on the cluster dynamics and on the individual masses that result
in a stellar mass spectrum. Further stellar interactions, including binary
destruction and eventually cluster dissolution are also discussed.
