A two-pane outliner separates structure from content—the structure is "extrinsic" to the text. A tree structure with node titles is presented in one pane, and the text is shown in another. Since the structure is always clearly shown at all times separately from content, this format allows for a quick overview of the structure, and easy navigation. The drawback is that since only one node's worth of text is shown at one time and navigation has the additional step of crossing panes, the structure is more rigid, making editing across nodes more difficult. This view is similar to many file browsers and email programs (which can be thought of as three-pane outliners). This type of structure is useful also as a document management tool where the second pane is a document in place of textual information.