StackLayout - first element in the beginning, second in the center

Hello! I want to achieve in Xamarin Forms the following layout - on the page I want to have first element at the beginning of the page and second element exactly in the middle of the page. I was trying something like this:

<StackLayout>
    <StackLayout VerticalOptions="Start">whatever</StackLayout>
    <Grid VerticalOptions="Center">whatever 2</Grid>
</StackLayout>

But it is not working. The grid is not in the center of the screen but it is close to StackLayout. How can I achieve the desired effect?