what is a non superimposable mirror image?

Question

http://en.wikipedia.org/wiki/Stereogenic

Answer 1

Unless a mirror image has perfect "left-to-right" symmetry and is the same size as the original image, it will be "non superimposable". Copy any image on a copy machine twice. Turn one of the copies over to create a "mirror image" and place the flipped copy on top of the first copy. Hold both up to the light (or copy the "mirror image" copy on transparent film) and see if they can be superimposed. Try this with simple vertical, horizontal, and diagonal lines to see what is happening.

Answer 2

cant be placed on top of another.. its not identical