Exoplanet observations have revealed a wealth of data that has to be explained via planet formation simulations. Past simulations focused mainly on the mass-orbital distance distribution of exoplanets. 

However, recent detailed observations have allowed to constrain planetary masses and radii to such detail, that the bulk composition can be derived, giving new constraints to planet formation models. 

Of particular interest is the water content of close-in super-Earths and sub-Neptunes, because the water content is an important tracer of the formation history of planets as well as of great importance for the search of life on other planets. 

In this talk, I will outline the main ingredients of planet formation simulations, focusing on the core accretion scenario, with a particular focus on the composition of planets. In particular I will highlight the importance of water, not only for the composition of planets, but also for the formation pathway (growth and migration) of the planets themselves.