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It has been recently proposed that it is possible to build microstates for two-sided Schwarzschild black holes by employing matter shells in the interior of the black hole. This procedure seemingly produces an arbitrarily large number of different microstates, creating a tension with the Bekenstein-Hawking entropy calculation which is solved by considering Euclidean wormholes. In this talk, I will argue that this construction is completely universal, and it can be extended to charged and rotating black holes, including the extremal and near-extremal solutions.