Some embodiments include an integrated assembly having a source structure, and having a stack of alternating conductive levels and insulative levels over the source structure. Cell-material-pillars pass through the stack. The cell-material-pillars are arranged within a configuration which includes a first memory-block-region and a second memory-block-region. The cell-material-pillars include channel material which is electrically coupled with the source structure. Memory cells are along the conductive levels and include regions of the cell-material-pillars. A panel is between the first and second memory-block-regions. The panel has a first material configured as a container shape. The container shape defines opposing sides and a bottom of a cavity. The panel has a second material within the cavity. The second material is compositionally different from the first material. Some embodiments include methods of forming integrated assemblies.