Any chemical compound showing polymorphism can crystallize with different internal lattices that will give correspondingly different external crystal morphologies, different optical crystallographic properties, and different physical properties. Ludwig and Adelheid Kofler and their successors in Innsbruck, Austria, along with Walter C. McCrone and his successors in the U.S., expounded the topic of polymorphism, especially as it was investigated with the polarized light microscope equipped with a hot stage.