Photochromism

Okay kiddo, have you ever seen glasses or sunglasses that change color when you go outside? That's called photochromism!

Photochromism is when a material changes color when it's exposed to light. You see, light is made up of tiny things called photons, and when those photons hit the material, it can cause the color to change.

So when you go outside and the sun shines on your glasses or sunglasses, the photons from the sun change the chemicals in the lenses and make them get darker. This helps protect your eyes from the sun's bright light.

But when you go back inside where it's not as bright, the lenses start to become clear again because there aren't as many photons around to make them dark.

It's kind of like when you wear a mood ring and it changes colors based on how you're feeling. Except with photochromism, it's all about the light!