We all know that mankind can't live without air, food and water...the same is true of salt. The salt on your table is a key to unlocking the story of our planet and the cosmos. Big History reveals how this simple molecule underpins our civilization, launched wars, built monuments like the Great Wall of China, sparked revolutions from India to France...and it's even the substance that makes up our thoughts.

The horse has been a revolutionary animal in unexpected ways. It has changed how we speak, what we wear, and sets the hidden limit for the size of our most massive empires. It's a story that spans the cosmos, from the Big Bang, to the Sun, to a changing planet that turned the horse into man's best friend in the animal kingdom.

This episode asks why mankind is gold crazy, and discovers there's a hard-wired reason we lust after it, and a microscopic explanation for why it shines. We reveal how the science behind our favorite metal drives men across oceans and continents, and how a difference in the way it's used in each hemisphere leads to a clash of civilizations.

Reveals how cold has the power to turn men into Barbarians, spark history's longest running war, and create the concept of race. After the heat of the Big Bang, cold creates the Universe and the planet as we know it. For thousands of years on Earth, cold controls the fate of our species by changing our bodies, our skin, and even the metals we use to fight our wars. When we finally take control of the cold, we learn to dominate the planet.

From the Great Pyramid at Giza to the towering skyscrapers of today, humans have engineered massive constructions for at least 5,000 years. But why? How do biology and human emotions affect our desire to build gigantic structures? Why were the earliest mega-structures almost always pyramids? Why do people have the urge to build tall, and how do mega-structures on earth echo a basic principle embedded in the very structure of the universe?