Polarized light microscopy brings out incredible colors in chemicals. Have a look at Bromine under the microscope.
Holmium (a metal) looks fairly interesting by polarized light microscopy.
Benzoic Acid is a simple aromatic carboxylic acid, with a crystalline structure that lights up in wonderful colors.
Polarized light Microscopy typically requires optically active materials to make the best images, follow some of the experiments I have been conducting to determine...