* Fish scales contain guanine crystals, which are responsible for their iridescent shimmer. Guanine reflects light in a way that creates the shimmering effect we see in fish scales.
* Lipstick often contains guanine, too! It's used as a pearlescent pigment to give lipstick a shimmering, iridescent finish.
So, next time you admire the shimmer of a fish in the water or see the gleam of a glittery lipstick, remember that they both share a common ingredient - guanine!