Have you ever wondered about how amazing cuttlefish are? No? Well then, take a seat.
These cuter versions of Cthulhu are not fish, but instead cephlapods and are therefore related to squids, octo(puses/pi/podes), the extinct ammonites, and nautiluses.
But where does the cuttle come from? Well, cuttlefish have cuttlebones! You read that correctly. While early molluscs had a hard external shell, the cuttlefish evolved to have an internal shell.
The cuttlebone is a porous structure made of argonite, which is an allotrope of calcium carbonate (MSE 102 has not failed me yet). They use it for depth control, but it comes at a price: Go too deep, and the structure implodes from the pressure! 
Having lost a hard *outer* shell, the cuttlefish needed to evolve new defense mechanisms. Therefore, they became masters of disguise! With chromatophores that can be stretched to change colour, and with papillae that create texture, even the metamaterials people must bow in awe.
They also have an amazing metal-like sheen at times, created by nano-crystalline iridophores, which diffract light to achieve this. Beneath those, there are leucophores, which just reflect light and allow for them to achieve visual depth (Like using the shade tool in Photoshop)!
On top of that, these creatures are super intelligent! Having the largest brain-to-body mass ratio of any invertebrate, they outsmart dolphins (who happen to love eating them), and hypnotize their prey with a dazzling colour show before striking them!
Those colours can also be used for communication, having over 40 to 100 different visual signals to choose from (More than some people's vocabulary)! These are achieved by altering colour, texture, posture, movements, and even iridescence.
One reason that they might have tended towards this over time is their mating habits. While the larger males tend to fight each other over mating rights, the smaller males *pretend to be female*, and swim right up to the female when no one is looking.
The female mates with several different males, then they get to choose whose sperm they fertilize their eggs with. The males get no choice in the matter (#girlpower). They almost always go for the smaller and less aggressive males (As proven by cuttlefish paternity tests).
You might be wondering, why have I never heard of these things? Well, in a way, you have. Sepia is called that because the original cuttlefish-sourced brown ink used by the Romans was named after the Greek word for cuttlefish (σηπία). To be fair, it is all Greek to me. *Beat*
I hope that you have enjoyed this cephalopod filled adventure, and now appreciate these mighty sea aliens! I deeply encourage everyone to learn even more about them, since they are *amazing*!
