Wikis are popular tools commonly used to support distributed collaborative work. Wikis can be seen as virtual scrapbooks that anyone can edit without having any specic technical know-how. The Wikipedia is a agship example of a real-word application of wikis. Due to the large scale of Wikipedia it's dicult to easily grasp much of the information that is stored in this wiki. We address one particular aspect of this issue by looking at the revision history of each article. Plotting the revision activity in a timeline we expose the complete article's history in a easily understandable format. We present WikiChanges, a web-based application designed to plot an article's revision timeline in real time. WikiChanges also includes a web browser extension that incorporates activity sparklines in the real Wikipedia. Finally, we introduce a revisions summarization task that addresses the need to understand what occurred during a given set of revisions. We present a rst approach to this task using tag clouds to present the revisions made.