How to... Rectangle panel?

Hi,

I would like to design an overview of kpi's which looks like tiles.

I've got a gridlayout with 2 rows and 3 columns. width and height ist set to auto because the application should always use the complete Display.

To create the tiles i have placed a Panel into the cell of the grid with also width and height set to auto.

Now i want to have that the Panel always looks like a rectangle with same width and height.

How can I achieve this? Does it work with CSS? Could you give me an example?

Thanks in advance.

Regards

Christoph