Go diving into the intertidal waters of the Great Barrier Reef along the northeastern coast of Australia, and you might happen upon a tiny octopus, no more than the size of your hand. Perceiving ...

Blanket octopus pairs are some of the undersea world’s oddest couples. What’s so startling is the size difference: Males are about the size of a walnut—less than an inch long—but some ...

Your guide—a man named Amba—makes a hand sign that shows he’s ... such as the ability to use tools, often don’t make much sense for an octopus: Its whole body is a tool.