To split a single cell in Excel 2007, follow these steps:

1. Select the cell that you want to split.
2. Click on the Data tab in the ribbon at the top of the screen.
3. In the Data Tools group, click on the Text to Columns button.
4. In the Convert Text to Columns Wizard that appears, select Delimited and click Next.
5. In the next screen, select the delimiter that you want to use to split the cell. This could be a comma, a space, a semicolon, or any other character that separates the data in the cell. You can also preview the results in the Data preview section.
6. Click Next and choose the format for each column that will be created. You can choose General, Text, Date, or Special formats.
7. Click Finish to split the cell into multiple columns.

Note: If you have any macro or Visual Basic code, wrap it in the tags.