A microelectronic device comprises a stack structure comprising vertically alternating conductive structures and insulating structures arranged in tiers, the tiers individually comprising one of the conductive structures and one of the insulating structures, a staircase structure within the stack structure and having steps comprising edges of at least some of the tiers, conductive contact structures on the steps of the staircase structure, support pillar structures laterally offset in at least a first direction from the conductive contact structures and extending through the stack structure, and bridge structures comprising an electrically insulating material extending vertically through at least a portion of the stack structure and between at least some adjacent support pillar structures of the support pillar structures. Related memory devices, electronic systems, and methods are also described.