Consider the spider: eight legs, eight eyes and a brain the size of a poppy seed. These are some of nature’s most amazing and charismatic creatures, and yet we know so little about their worlds. Paul Shamble discusses the lives, habits and marvelous morphologies of these animals—from sensory structures and cognition to locomotion and behavior. Understanding these creatures helps us better understand evolution and diversity—and leads us to ask what it means that even tiny animals inhabit complex lives.