How to add a magnification segment of an image to the original size image

[Ofnuts]

Same as Rich, you have two images, and the 1st is a clickable link for the second. You can detect that you clicked on the PiP using an "imagemap". In a primitive way this is a second identical HTML page with just the picture changed, a more evolved technique would use Java script to change the initial page to replace the 1st image by the second (and change the link to another JavaScript that put back the initial image).