You can merge or split cells using the Merge cells and
Split cell buttons on the Home tab, in the Table group, as well as the corresponding items in the context menu.
Merge cells
When merging two or more cells, only the data and formatting (fill, font, etc.) from the upper left cell of the selected range will be saved. Data from all other cells will be irretrievably lost.
To merge cells, select adjacent cells, then use one of the methods:
–Click Merge cells.
–From the context menu, select Merge cells.
–Press the keyboard shortcut Alt+Ctrl+M (Option+Cmd+M).
Split a cell
You can only split a previously merged cell.
When you split a previously merged cell, it is split into the original number of rows and columns. The data from the merged cell will be placed in the upper left cell of the new range; the other cells will be empty.
To split a cell, select the cell, then use one of the methods:
–Click Split cell.
–From the context menu, choose Split cell.
–Press the keyboard shortcut Alt+Shift+M (Option+Shift+M).