Nature

From the tiniest single-celled organisms to the giants that roam the Earth, the animal kingdom is one that fascinates us all. Every day we learn more about the creatures we share the planet with, all 1.5 million-plus of them, and that's just the ones we have discovered so far. Whether we keep them as pets, eat them for food or study them for science, our relationship with animals is complex, but is part of the very nature of what makes us human.