We just learned about the Cephalopod Ink.
Another part of many cephalopods is the Chromatophore.
Cephalopods have little sacks in their skin called cytoelastic sacculus, that are filled with something called pigment granules.
That's a lot of big words, but it basically means they have tiny bags of color all over their skin, and they use muscles to squish out more color or less color to change the way they look.
(from: wikipedia - Chromatophore)
Kid Facts - Blast from the past: Rhacophorus
