You can view the "raw" HTML, CSS and JavaScript of any Pen by appending a URL extension. That means you can also use a Pen as an external resource of any other Pen, or Project!

We've seen some slight confusion here though, specifically in regards to caching. If you make a change to the Pen that is being used as a resource, you need to save it for the changes to be reflected by whatever is using that resource. Without saving it, the old code will be cached.

Here's a little video that shows how it all works: