The octopus is a highly intelligent and deeply mysterious creature. It changes colour as quickly as it can move, and it thinks with its tentacles.
Marine biologist David Scheel has had a life-long fascination with them. He's discovered new species and has learned to understand how they communicate with signals.
Dr Scheel's new book Many Things Under a Rock: the Mysteries of Octopuses reveals complex emotional beings that can teach us about ourselves.