What's the difference between a squid and an octopus?

Cephalopods are a group of marine creatures who all have a big head, a set of arms or tentacles, and can squirt ink. This group includes animals like squids and octopuses, but how do you know which is which? Marine biologist Sarah McAnulty gave us a few things to look for.  If you’ve got a Moment of Um question inked in your brain, send it our way at BrainsOn.org/contact, and we’ll search for the answer. See omnystudio.com/listener for privacy information.