>I have tested another solution, two ScrollViewers. The outermost ScrollViewer is needed because the Window is greather than the regular 800 x 600 size.
>Another ScrollViewer That Contents all the expanders, but It is never displayed, the Grid is never cliped to its container size.
>
>

><ScrollViewer HorizontalScrollBarVisibilitty="Auto" VerticalScrollBarVisibility="Auto">
>    <TabControl>
>        <TabItem>
>            <Grid>
>                <Grid.ColumnDefinitions>
>                    <ColumnDefinition Width="300"/>
>                    <ColumnDefinition/>
>                </Grid.ColumnDefinitions>
>                <StackPanel>
>                        <!-- Main Content -->
>                </Stackpanel>
>                <ScrollViewer Grid.Column="1" HorizontalScrollBarVisibilitty="Disabled" VerticalScrollBarVisibility="Auto">  // Allow Vertical Scrolling
>                    <StackPanel>
>                         <Expander>
>                            <!-- Description 1 -->
>                         </Expander>                     
>                         <Expander>
>                            <!-- Description 2 -->
>                         </Expander>                     
>                         <Expander>
>                            <!-- Description 3 -->
>                         </Expander>                     
>                    </StackPanel>
>                <ScrollViewer/>
>            </Grid>
>        </TabItem>
>        ...
>    </TabControl>
></ScrollViewer>
>
>

>
>Any idea of how to set the Grid´s Height to its container Height?
>
>Thanks

If your Grid is contained in a ScrollViewer with vertical scroll enabled then it is not constrained to any height (i.e. it can make itself as large as neccessary) . Try setting the outer ScrollViewer VerticalScrollBarVisibility to 'Disabled'