Energy density decreases asymptotically with time. Can view as eras. Some things not stable at high energy become stable, e.g. quarks and elementary particles. Eventually, the environment is not hostile to their existence. Then, the first hierarchies appear as an emergence system, i.e. protons.
Hierarchies become stable.
Then more complex atoms Then inorganic molecules, organic molecules, etc. Always with decreasing energy. Evolution is then a sign of complexification Hierarchy is a sign of discontinuous energy gradients. All interactions take place within strata. Between the strata, there is nothing observable.