The invisibility cloak
« They are elvish robes certainly […] And you will find them a great aid in keeping out of the sight of unfriendly eyes, whether tou walk among the stones of the trees »
J.R.R Tolkien, The lord of the rings, Part one, The fellowship of the ring, Chapter8, Farewell to Lorien
During their journey, the Fellowship of the Ring receives invisibility cloaks from the Lorien Elves. These garments, 'made of a silky, light and warm fabric' (SDA, Book 1), allow one blend into the landscape and escape from enemies. This camouflage strategy, called "cryptic mimicry", is common to many animals.
Indeed, many insects have a coat or shape resembling leaves or branches, sometimes mimicking their colour or patterns, to escape the sight of predators... or indeed, to avoid being spotted by their potential prey.
On the other hand, contrary to popular belief, the chameleon does not change colour with its environment but according to its mood... a visual means of communicating with its fellow creatures.