Yes, it is possible to format cells in Excel to display data to 3 significant figures. Here's how you can do it:

1. Select the cells that you want to format.
2. Right-click on the selected cells and choose "Format Cells" from the context menu.
3. In the "Format Cells" dialog box, select the "Number" tab.
4. In the "Category" list, select "Custom".
5. In the "Type" field, enter the following format code:
   Formula:

   0.###E+0 

6. Click "OK" to apply the format to the selected cells.

This format code will display numbers to 3 significant figures and will use scientific notation for very large or very small numbers. For example, the number 1234 will be displayed as 1.23E+3, and the number 0.00123 will be displayed as 1.23E-3.

Note that this format code will always display a decimal point, even if the number is a whole number. If you want to remove the decimal point for whole numbers, you can use a conditional formatting rule to apply a different format to whole numbers.