When two or more adjacent cells are merged, one greater cell is displayed across multiple column and rows. To merge adjacent cells do the following steps:
1– Select more than one adjacent cell e.g. cell A1 and B1 below.
Both cells A1 and B1 will merge into a larger single cell.
3– To unmerge, either press Ctrl + Z or go to the Home tab and select the Merge & Center option again.