Creating a resizeable (endless) scrollview in Unity3d

In recent versions of Unity, a “Scrollview” UI element has been introduced. It’s very useful, but one thing that wasn’t obvious (to me, at least) was how to use it for something that has potentially infinite content. In my case, I have a message window which has text added to it at various points during the game. I wanted that text to be added to the bottom of a scroll view, but have the previous text still accessible via the vertical scroll bar.