Watch: The hidden cost of war

If the population of the world was only 100 people, what would society look like?

It’s easy to extend their usefulness by turning them into a flower pot, watering can, or pencil holder.

We calculated the land area needed to supply the entire United States with solar power.

They are the most deadly weapon ever created by man. How many nuclear weapons are there? Who has them? Here are nukes by the numbers, the explosions and the destruction.

How does kissing affect our brains? Which way do most people tilt their heads? And how did the 'X' come to stand for a kiss?