Movie special-effect gurus are forever trying to invent more compelling creatures from other planets, hoping to terrorize our imaginations. To do this, they often draw from the natural world, and few creatures fit the bill more than the cephalopods: shapeshifters, with three hearts, blue blood and holes in their brains. But while they might look like creatures from another galaxy, these aliens have called Earth home for hundreds of millions of years. In our quest to find intelligent life, we search among the stars, but perhaps we should be looking closer to home. The octopus, squid and cuttlefish are some of the most intelligent creatures in the animal kingdom. They have colonized all of the world’s oceans and are widespread in even the darkest corners of the abyss. So, forget Hollywood; there are aliens in the deep.