" A voltmeter picks up the fish’s electric pulse. A light, actually powered by the eel’s electricity, flashes across a panel built on top of the tank to show when the eel is hunting or stunning prey, and this quickly attracts attention. On this morning, Scott and I had the eel tank to ourselves. Even though Scott had just fed some worms into the Deployer, the three-foot, reddish-brown eel was immobile. I wondered if he was just watchfully waiting. “Look at his face,” Scott said. “No, that eel is catching some serious Zs.” A worm dropped right near his head, and still the fish didn’t move. The eel was fast asleep. Then suddenly, we saw the voltmeter flash. “What’s going on?” I asked Scott. “I thought the eel was asleep.” “He is asleep,” Scott answered. And then we both realized what was happening. The eel was dreaming. "

― Sy Montgomery , The Soul of an Octopus: A Surprising Exploration Into the Wonder of Consciousness