Dogs have long been dependable companions by our sides. But it wasn't always that way, and a look at their closest living relative, the wolf, makes it clear why. Research into dog domestication and intelligence offers clues into what the human-dog relationship is all about. And analyzing dogs' brain activity and genes may even help answer the question of whether dogs are in it for the food—or if they really love us.

From fruit flies to whales, virtually every animal sleeps. But why? Why do we need to spend nearly a third of our lives in such a defenseless state? Scientists are peering more deeply into the sleeping brain than ever before, discovering just how powerful sleep can be, playing a role in everything from memory retention and emotional regulation to removing waste from our brains. So why are we getting so little of it?