Interpolation is a mathematical way of regenerating missing or needed information. Let's say that an image needs to be scaled up by a factor of two, from 100 pixels to 200 pixels. We can do this by interpolation. The missing pixels are generated by interpolating between the two pixels that are on either side of the pixel that needs to be generated. After all of the "missing" pixels have been interpolated-presto!-200 pixels exist where only 100 existed before, and the image is twice as big as it used to be. There are many methods of interpolation; the method described here is an example of simple averaging.