If you do not want to wrap, then clicking on the horizontal / vertical scroll bar is another option that you might want to explore. Reading the question, I think that textwrapping might be more appropriate (it doesn't seem like you want to hide something), but the options are always nice.
<ScrollViewer Height="30"> <TextBlock Width="30" TextWrapping="Wrap">HElooooooooooooooooooooooooooooooooooooo</TextBlock> </ScrollViewer>
EDIT: combines word wrap and scrollviewer.
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