Merge and unmerge cells
You can't split an individual cell, but you can make it appear as if a cell has been split by merging the cells above it.
Select the cells to merge.
Select Merge & Center.
Important: When you merge multiple cells, the contents of only one cell (the upper-left cell for left-to-right languages, or the upper-right cell for right-to-left languages) appear in the merged cell. The contents of the other cells that you merge are deleted.
Select the Merge & Center down arrow.
Select Unmerge Cells.
You cannot split an unmerged cell. If you are looking for information about how to split the contents of an unmerged cell across multiple cells, see Distribute the contents of a cell into adjacent columns.
After merging cells, you can split a merged cell into separate cells again. If you don't remember where you have merged cells, you can use the Find command to quickly locate merged cells.