The structuration of the interstellar medium into molecular clouds and the inner structure of these clouds are fundamental for subsequent star formation, the propagation of stellar feedback and the enrichment of galaxies. These properties are largely set at galactic scales, by a complex interplay of multi-scales and multi-physics processes. Understanding this scale coupling and its dependance on the environment is thus crucial to describe star formation. In this talk, I will show how the diversity of galactic environments imprint the interstellar medium, within our Milky way, and from galaxy to galaxy, across cosmic time. I will illustrate this point with a series of simulations, and I will discuss the possible implication in either the diversity, or the universality of small scales properties, like the IMF.