"Tail problem." In all collapse theories, the wave function is never fully contained within one (small) region of space, because the Schrödinger term of the dynamics will always spread it outside. Therefore, wave functions always contain tails stretching out to infinity, although their “weight” is the smaller, the larger the system. Critics of collapse theories argue that it is not clear how to interpret these "tails", since they amount to the system never being really fully localized in space. Supporters of collapse theories mostly dismiss this criticism as a misunderstanding of the theory, as in the context of dynamical collapse theories, the absolute square of the wave function is interpreted as an actual matter density. In this case, the "tails" merely represent an immeasurably small amount of "smeared-out" matter, while from a macroscopic perspective, all particles appear to be point-like for all practical purposes.