The cosmological one is maybe easier to realize: it considers, the current Universe generation is formed by interior of giant dense collapsar, which is behaving like black hole from outer perspective. This collapse was followed by phase transition, which proceeded like crystallization from over-saturated solution by avalanche-like mechanism. During this, the approximately spherical zones of condensing false vacuum have intersect mutually, and from these places the another vacuum condensation has started (a sort of nucleation effect). We can observe the residuum of these zones as a dark matter streaks. The dodecahedron structure of these zones should corresponds the E8 group geometry, as being observed from inside (i.e. from past perspective due the Universe "expansion").
The second interpretation of E8 is relevant for Planck scale, i.e. for outer perspective (the future). The dense interior of black hole is forming the physical vacuum, which is filled by spongy system of density fluctuations, similar to nested foam. Such structure has even a behavior of soap foam, because it gets more dense after introducing of energy by the same way, like soap foam shaken inside of closed vessel. Such behavior leads to the quantum behavior of vacuum and particle-wave duality. Every energy wave, exchanged between pair of particles (i.e. density fluctuations of foam) is behaving like less or more dense blob of foam, i.e. like gauge boson particle. Every boson can exchange its energy with another particles, including other gauge bosons, thus forming the another generation of intercalated particles.
Therefore the E8 Lie group solves the trivial question: "Which structure should have the tightest lattice of particles, exchanged/formed by another particles?". And such question has perfect meaning even from classical physics point of view! Such question has a perfect meaning in theory, describing the most dense structure of inertial particles, which we can ever imagine, i.e. the interior of black hole. AWT inteprets a rotation of Lie group in general reference frame, which leads to another particle generation as a Penrose-Terrell effect, formalized in Wick rotation approach.