Abstract: I will discuss the possibility that certain high-energy holographic CFT states correspond to black hole microstates with a geometrical behind-the-horizon region, modelled by a portion of a second asymptotic region terminating at an end-of-the-world (ETW) brane. The ETW boundary geometry takes the form of a closed FRW spacetime, and, in many cases, this behind-the-horizon physics can be probed directly by looking at the time dependence of entanglement entropy for sufficiently large spatial CFT subsystems. We study states defined via Euclidean evolution from conformal boundary states and give specific predictions for the behavior of the entanglement entropy in this case. Analogous calculations for the SYK model yield qualitative agreement with our expectations. A fascinating possibility is that for certain states, we might have gravity localized to the ETW brane as in the Randall-Sundrum II scenario for cosmology. In this case, the effective description of physics beyond the horizon could be a big bang/big crunch cosmology of the same dimensionality as the CFT and the black hole microstate would give a precise, microscopic description of this cosmological physics. I will discuss nearly finished work with Stefano Antonini in which we realize precisely this scenario in Einstein-Maxwell theory and demonstrate gravity localization behind the horizon.