Grid - more than one in a layout

being new to Vaadin i might well have shot me in the foot - or Grid did:
Using valo-theme, i try to put two Grids on a page. They overlap, whatever i try.
In firefox debugger i can see, that there is one tablewrapper-element containing both Grids.
Both Grids have a header (grid-caption), only the header of the first Grid is visible.
i tried to put the Grids in nested layouts, no success.
All the demos show just one Grid on one page…
Has anyone put two Grids vertically on one page ? Or do they interfere somehow?

What layout did you use to arrange the Grids? The following should work fine:

VerticalLayout layout = new VerticalLayout();

layout.addComponents(firstGrid, secondGrid);