There's an easy way to understand chirality. Hold out your hands, palms facing each other. Imagine that each hand is the chemical structure of a molecule. Most complex molecules are chiral. Like your hands, the two structures of chiral molecules - in sugars, they're referred to as D and L, from the Latin dexter and laevus - differ only in the arrangement of their elements. Put your hands together and they seem to match exactly. In the same way, the common sugar D-glucose is the mirror image of L-glucose, its rare counterpart. But put your hands down one on top of the other, both facing down, and you'll see that they're not identical at all; they're what chemists call non-superimposable.