Table, Modify, Split Cells Dialog Box
The Split Cells dialog box enables you to split existing table cells into multiple columns or rows. Only the selected cells are split. For example, if you split one cell into two rows, the remaining cells in the original row will span both rows.
To split table cells into columns or rows
In Design view, select the table cell or cells that you want to split.
In the Table menu, click to Modify and then click Split Cells.
The Split Cells dialog box is displayed.
Select the options that you want, and then click OK.
The selected cell or cells are split into multiple columns or rows.