Octopuses have been captivating humans for as long as we have been catching them. Yet for all of our ancient fascination and modern research, we still have not been able to get a firm grasp on these enigmatic creatures. Katherine Harmon Courage dives into the mystifying underwater world of the octopus and reports on her research around the world. She reveals, for instance, that the oldest known octopus lived before the first dinosaurs; that two thirds of an octopus's brain capacity is spread throughout its arms, meaning each literally has a mind of its own.