Integrated assemblies and methods of forming integrated assemblies

An integrated assembly, comprising:

• a source structure;
• a stack of alternating conductive levels and insulative levels over the source structure;
• cell-material-pillars passing through the stack;
• the cell-material-pillars being arranged within a configuration which includes a first memory-block-region and a second memory-block-region;
• the cell-material-pillars including channel material;
• the channel material being electrically coupled with the source structure;
• memory cells along the conductive levels and comprising regions of the cell-material-pillars;
• and
• a panel between the first and second memory-block-regions;
• the panel having a first material configured as a container shape having a bottom surface contacting the source structure and having outer sidewalls, a width of the container shape being substantially uniform along an entirety of the outer sidewalls;
• the container shape, along a cross-section, defining opposing sides and a bottom of an interior cavity, an uppermost region of the interior cavity being wider than a remaining region of the interior cavity;
• the panel having a second material within the interior cavity, with the second material being compositionally different from the first material.