To format a number to display in scientific notation:
Select the Cells command from the Format menu (or right-click and select Format Cells).
Select the Number tab in the "Format" dialog box.
Select Scientific from the numbers list and then set the decimal places as described in Formatting a number.
Ability defaults to Scientific format if the number is too big (or small) to display with significant precision in the width of the current cell.
Note: scientific format coverts the original number into a base number, between 1 and 10, multiplied by a power of 10. This is useful for working with very large or very small numbers. For example, 1 meter is defined as the distance light travels in 0.000000003335640952 seconds. Entering such a value is hard on the eye. Selecting scientific format gives you a simplified display of 3.34E-09 (which is 3.34 x 10-9).