Abstract: I will overview recent advancements in the study of galaxy clusters, both as astrophysical objects and as cosmological tools, using detailed hydrodynamic simulations.  I will discuss how improvements in the numerical description of galaxy formation processes, related to star formation and gas accretion onto super-massive black holes, is leading to the production of realistic population of clusters from simulations. These “artificial” clusters can then be used to quantitatively assess systematics in their application as tools for measuring cosmological parameters. After comparing results from simulations to X-ray and SZ observations of galaxy clusters, I will critically discuss the challenges that the next generation of simulations will have to face with.