The most important, lowermost pillar, is the photochromic crystal. It has a unique chemical structure that is characterized by a single bond that brings the entire molecule to a “full energy state”. However, this bond can be temporarily broken or changed through continuous absorption of another frequency of light. This lowers the “energy state” of the molecule, allowing it to absorb more energy through light that turns it opaque. In the absence of the “triggering light source”, the molecule immediately reverts back to its transparent state.

         It is theoretically possible to engineer a photochromic crystal with a weaker bond, by using a bigger element, so that the bond is farther from the nucleus, and vice versa. Thus we could create photochromic crystals that respond to different frequencies of light, as well as being opaque to different frequencies of light.