Windows Phone ScrollViewer not scrollable?

I am currently working on yet another application. In that application I have two pages, the MainPage where I can choose a certain phrase. Choosing one of them navigates me to my second page, where I have three TextBlocks. The length of the text varies, depending on the phrase I chose in the first page.

No problem, I thought. I’ll just put my TextBlocks in a StackPanel, And I nicely can put a ScrollViewer around the TextBlocks:

<StackPanel>
    <ScrollViewer>
    <TextBlock Name="TextBlock1"
               Height="100"
               FontSize="24"
               TextWrapping="Wrap"/>
    </ScrollViewer>
    <ScrollViewer>
    <TextBlock Name="TextBlock2"
               Height="280"
               FontSize="28"
               Margin="10"
               TextWrapping="Wrap">
    </TextBlock>
    </ScrollViewer>
    <TextBlock Name="TextBlock3"
               Height="120"
               FontSize="22"
               Foreground="Red"
               TextWrapping="Wrap"/>
</StackPanel>

Well, what sounded nice in theory did not work out. When I ran the application, I could see there is a ScrollViewer, but somehow it just bounced back to the start point whenever I tried to scroll.

The solution was quite easy in the end. I replaced the StackPanel with a Grid:

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="100" />
        <RowDefinition Height="280" />
        <RowDefinition Height="120" />
    </Grid.RowDefinitions>
    <ScrollViewer>
    <TextBlock Name="TextBlock1"
               FontSize="24"
               TextWrapping="Wrap"/>
    </ScrollViewer>
    <ScrollViewer>
    <TextBlock Name="TextBlock2"
               FontSize="28"
               Margin="10"
               TextWrapping="Wrap">
    </TextBlock>
    </ScrollViewer>
    <TextBlock Name="TextBlock3"
               FontSize="22"
               Foreground="Red"
               TextWrapping="Wrap"/>
</Grid>

Now I can scroll in the two TextBlocks that I need.