If you're a tiny crustacean living in the dangerous deep sea, the best way to defend yourself is to know how to hide. Some sea creatures can camouflage, pretend like a coral, an algae, or maybe sand. Other sea creatures are lucky enough to have transparent shells, enabling them to swim freely under the sea.
Laura Bagge, a marine biologist and doctoral student at Duke University is interested with the sea species Cystisoma. It is one of the seven types of hyperiid amphipods, which are a type of invisible crustaceans.
According to Bagge, Cystisoma are different from other hyperiid species because its legs were covered by extremely tiny structures, called nanoprotuberances. These tiny structures are presumed to be bacteria which help Cystisoma hide from predators by giving it an antireflective coating.
Though, invisible sea creatures are very difficult to see under the ocean, their defense mechanism has a weakness. Once reflected with sunlight, moonlight, or luminescence from predators, they will be seen as the light passes slowly through their invisible shells.
“Any reflections that hit you from above are going to make you just flash really brightly against the darker background,” says Bagge in an interview
Cystisoma are a bit different from other species of hyperiid, according to Bagge. Because of their bacteria friends attached to their legs, they make a more effecient "cloak" for hiding.
According to scientists, these tiny structures of Cystisoma have “corneal nipples.” It reduces the glare of light by reflecting it off due to its mountain-like shape. Experts suspect that the bacteria and Cystisoma are sharing a mutual relationship, which I think is beautiful.
Now, what I conclude is that Harry's invisibility cloak is made up of this same bacteria because that's the only explanation behind it.