What is the universe made of? If you answered stars, planets, gas and dust, you'd be dead wrong. Thirty years ago, scientists first realized that some unknown dark substance was affecting the way galaxies moved. Today, they think there must be five times as much dark matter as regular matter out there. But they have no idea what it is ? only that it's not made of atoms, or any other matter we are familiar with. And Dark Matter is not the only strange substance in the Universe ? a newly discovered force, called Dark Energy, seems to be pushing the very fabric of the cosmos apart.