This is a penny.  We all know how big it is, how much space it takes.  But what about a thousand pennies?  A million pennies?  Can you visualize it? 

The MegaPenny Project might be able to help you realize just how big some numbers (like a billion) really is.  For example:

This is a thousand pennies.

This is a million pennies.

This is a hundred million pennies.

And this is ten billion pennies.

Pretty cool, huh?