Dogs have been our companions for thousands of years. Do they really love us, or are they just in it for the food? Scientists test wolf intelligence, decode canine DNA, and peer into dogs' brains to find out what domestication really means.

Worshipped as a goddess, condemned as satanic, and spun into a stunning array of breeds, cats have long fascinated humans. But did we ever really domesticate them? And what can science tell us about our most mysterious companions?