The highest mountains on Earth are home to snow leopards, golden eagles, mountain goats, barnacle goslings, and gelada monkeys; only the toughest of animals can endure the extreme weather, scarce food supplies and limited oxygen on these peaks.

Delving beneath the surface of the Earth's oceans to uncover a world of extraordinary extremes, including crushing depths, stormy coasts, vast blue deserts, and crowded reefs; how seals fend off sharks; how orcas fight to survive.

In the grasslands, animals endure freezes, fires, floods, and droughts; bull elephants clash in mating battles; cheetahs and gazelles engage in a predator-and-prey dance in the Kenyan savanna; bison battle a blizzard while being pursued by wolves.