  The physical information encoded in the cosmological late-time wavefunction
of the universe is tied to its singularity structure and its behaviour as such
singularities are approached. One important singularity is identified by the
vanishing of the total energy, where the wavefunction reduces to the physics of
scattering in flat space. In this paper, we discuss the behaviour of the
perturbative wavefunction as its other singularities are approached and the
role played by the flat-space scattering, in the simplified context of the
class of toy models admitting a first principle definition in terms of
cosmological polytopes. The problems then translates into the analysis of the
structure of its facets, one of which -- the scattering facet -- beautifully
encodes the flat-space S-matrix. We show that all the boundaries of the
cosmological polytope encode information about the flat-space physics. In
particular, a subset of its facets turns out to have a similar structure as the
scattering facet, with the vertices which can be grouped together to form lower
dimensional scattering facets. The other facets admit one (and only one)
triangulation in terms of products of lower dimensional scattering facets. As a
consequence, the whole perturbative wavefunction can be represented as a sum of
product of flat-space scattering amplitudes. Finally, we turn the table around
and ask whether the knowledge of the flat-space scattering amplitudes suffices
to reconstruct the wavefunction of the universe. We show that, at least for our
class of toy models, this is indeed the case at tree level if we are also
provided with a subset of symmetries that the wavefunction ought to satisfy.
Once the tree cosmological polytopes are reconstructed, the loop ones can be
obtained as a particular projection of them.
