Recent years have witnessed the emergence of galaxy clusters as a fundamental cosmological and astrophysical tool.  In this talk I will review recent advances in the physics of clusters. I will focus on what can be learned from X-ray, Sunyaev Zel'dovich and lensing observations, and hydrodynamical numerical simulations. I will discuss some recent developments on the modeling of both dark matter and the intracluster medium, in particular with respect to the first determination of the intrinsic shape and physical parameters of both dark matter and the intracluster medium in triaxial galaxy clusters via a multiwavelength analysis. Next, I will discuss a method to determine of physical parameters in clusters, including gas temperature and peculiar velocities, via multi-frequency Sunyaev Zel'dovich observations and independent of X-ray observations. Finally, I will overview recent developments in the virialization region of clusters, which has recently raised a lot of attention because it offers a direct view of structure formation. In particular, I will present novel results on the physical properties of the intracluster medium at the cluster outskirts, including average emission measure, gas density and gas fraction, temperature, entropy and gas inhomogeneities.