What exactly are we looking at here? The veined octopus, also known as the coconut octopus, is one of the smartest animals on Earth, building shelters from seashells and coconut shells. If you peek inside, you may spot those telltale suction cups that cover the creature's eight limbs. These arms contain clusters of neurons, which make them particularly sensitive, and each arm can be used separately to perform complex tasks. Octopuses can also match the color—sometimes even the texture—of their environment, making them even more difficult to spot. There's lots more to learn about these fascinating animals, and World Octopus Day is a great day to do it. You could always start with the Academy Award-winning documentary 'My Octopus Teacher.'