This lecture discusses the Provision of Ancillary Services from Regional Energy Networks, focusing on characterizing the Reserve Provision Capability Area of Active Distribution Networks. It covers collaboration with Swissgrid, estimating the RPC area for reserve market offerings, linear modeling for DERS, and a scenario-based robust optimization method. The lecture concludes with next steps, including aggregating RPC areas at the TSO-DSO connection point and developing a methodology for re-dispatching DERS to provide ancillary services.