Stars are formed by the gravitational collapse of dense, gaseous and dusty cores within magnetized molecular clouds. Understanding the complexity of the numerous physical processes involved in the very early stages of star formation requires detailed thermodynamical modeling in terms of radiation transport and phase transitions. I will discuss the outcome of our spherically symmetric radiation hydrodynamic simulations with which we investigate the collapse of molecular cloud cores including the stages of first and second hydrostatic core formation. We investigate the properties of Larson’s first and second cores and expand these collapse studies for the first time to span a wide range of initial cloud masses from 0.5 Msun to 100 Msun. I will highlight the strong dependence of a variety of first core properties on the initial cloud mass. Furthermore, based on our new 2D radiation hydrodynamic simulations, I will discuss the impact of different cloud properties on the formation of early disks.