Huge distances, gigantic sizes, and long periods of time—astronomy is a BIG subject. We've brought learning about it down to size with this look at the big ideas you need to know. 

How much do you really know about our place in space? Test your astronomy knowledge with this interactive quiz. Don't worry, there's no grading—just a helpful look at the answers when you're done! 

That change jangling in your pocket is more than money—it's a record of where and when you live. Find out why coins are valuable clues for archaeologists. Then, design your perfect coin. 

Unlike humans, some animals can instantly change the color or pattern of their skin. Take a hands-on look at how the masters of disguise known as flounders can don several different looks.

Most of the deep sea is very dark, with little or no sunlight. But that doesn't mean marine animals are in the dark! Learn how these clever creatures create their own light.