How to Wrap text in merged cells

Select the merged cells that you wish to wrap text. Right-click and then select "Format Cells" from the popup menu.

 When the Format Cells window appears, select the Alignment tab and select the "Wrap text" checkbox.

 You will need to manually adjust the height of the row that contains the merged cells.

 In Excel 2010 there in no need to select "Format Cells" to wrap or merge the cells. In the " Home menu"  "Wrap text" and "Merge cells" appear in the tool bar . ( As shown in the image below)

( Click on the image to enlarge it)