Abstract: In this talk I will review the properties that classical (macroscopic) configurations of a physical system inherit from the underlying quantum (microscopic) configurations. A priori information of this type proves to be crucial in studying effective theories. As an example, consider the well-studied problem of deriving effective dynamical theories in many-body quantum mechanics. Clearly, this is possible only for classical configurations concentrated in the domain of well-posedness of the effective theory. Therefore, it is important to give sufficient microscopic conditions that would ensure macroscopic concentration on such domain. Another interesting consequence of this micro-to-macro analysis is that semiclassical states cannot be more entangled than the corresponding quantum states.