Assuming a general structure where DM belongs to a hidden sector, we determine in a general way the various ways DM could be produced in the early Universe thermal bath: standard freeze-out, secluded freeze-out, reannihilation, sequential freeze-in and freeze-in. Which production regime holds depends on the magnitude of the hidden sector interactions as well as of the portal interactions between the SM and hidden sectors. If time allows we will also discuss the general case where the portal interactions are negligible, so that both sectors have their own thermal bath, determining in this case what is the general domain of possibilities to account for the observed DM relic density.