Cuttlefish take camo to new heights. Not only can they change colors to blend in, but their psychedelic skin even puts chameleons to shame. Every square millimeter holds up to 200 color-changing chromatophores, layered atop other cells that reflect light. And below those, they also have tiny muscles that can mimic the texture of rocks and reefs (like this broadclub cuttlefish).
Cuttlefish aren't really fish — they're "cephalopods," a family of aquatic mollusks that also includes octopus and squid. Their appearance-altering skills go beyond mere camouflage, too, letting them glow wildly with color and light, as seen in this video clip: