In the previous chapters, we have learned how to create Node Content and apply minor editing to it. The level of control over the appearance of the text that we saw is fine if only some basic changes are called for (such as underlining a word here, making a word bold there, while retaining the default top-down paragraph style). However that's not always the case. Sometimes you may need to do something different that requires some customization to your Node Content, or perhaps to instances of similar Node Content.
Aside from the requirements affecting appearance, there are also times when a Node Content piece is a 'living' document, or 'content by committee'. In either case, it would be handy to have more than one version of the Node Content available—and you can, à la Revisions!