what molecules are the photochromic glasses lenses coated with?

[Quintana]

I just wonder what molecules are the photochromic glasses lenses coated with? How do they cause the lens go from dark to clear?

[Quinten]

As we know that photochromic lenses can turn dark in sunshine and fade away in door. That because the lenses contain organic (carbon-based) molecules that can react to light in a slightly different way. The molecules in the lenses can change their color and size when ultraviolet light strikes them. Though each molecule changes by only a fraction of a nanometre,there are many molecules in the lenses that can react in the same way, thus make the lenses turn dark and fade away quickly.