Keep child fixed size depending on parent.

Hope someone can help me with this issue.
I have created a gameboard which contains to areas (grids), the gameboard itself and the inventory area below. (Shown below as red).

These 2 grids are inside a parent panel. (shown below as blue)

Now my issue it how do I make the panel and the children inside dynamic so if a panel or screen is either wide or tall. (Shown below as green)


I really hope someone can either show or guide me in the right direction on this and thanks in advance

 

Try giving the top-level object in your board an Aspect Ratio Fitter component set to "fit inside parent".