It's mind boggling to think about how big and complicated the internet really is, even for adults. Google has put together a really cool animation called "The Story of Send" that explains what happens to your Gmail once you send it on its way, and it's a great tool to help explain to your kids how email gets from your computer to a recipient across the country or around the world.
A complex site with animation, videos and pop ups, it's pretty in depth look at how Google handles security, creates hardware, and their efforts to be environmentally efficient.
It's a neat look behind the scenes at how email moves in general and how Google specifically handles the huge amounts of data that passes through their servers. Click here to watch The Story of Send. Watching all of the videos takes about 30 minutes, but you can get the gist of it by following the animation in about 10.