Split cells are used to reformat tables quickly without shifting other cells over. When you split a cell horizontally, the cell divides from side to side, creating an additional row within the cell. When you split it vertically, it divides from top to bottom, creating an additional column within the cell. Splitting a cell diagonally splits it from one corner to another. Although there's not an option to split cells diagonally in the Layout tab in Word or PowerPoint, you can use other tools to divide the cell.
Click anywhere within the table to make the "Design" tab visible in Microsoft Word.
Click the "Design" tab under "Table Tools."
Go to the "Draw Borders" group and select "Draw Table."
Place your cursor at the top corner of the cell you want to split.
Click, hold and drag your mouse from the top, right corner of the cell to the opposite corner to split it diagonally.
Click the "Draw Table" button to deactivate the "Draw Table" option.
Microsoft Excel or PowerPoint
Click the "Insert" tab in Microsoft Excel.
Go to the "Illustrations" group and click "Shapes" to expand its options.
Select the "Line" option from the "Lines" section.
Place your cursor on the top, left corner of the cell you want to split.
Click, hold and drag your mouse towards the opposite corner to split the cell diagonally.