The lenses of color changing glasses can darken when sunlight shines. When the lighting weakens, it becomes bright again. This is possible because the crystals of Silver halide are working. Under normal circumstances, it can maintain perfect transparency of the lens. Under the irradiation of sunlight, the silver in the crystal separates, and the free silver forms small aggregates inside the lens. These small silver aggregates are irregular blocks with interlocking teeth, unable to transmit light but can only absorb it, resulting in the lens becoming darker. When the light is dark, the crystal forms again, and the lens returns to a bright state.