display subcaterogies when main category is clicke

[theman]

ok would like to use default osc install as example

 

i would like it if click on hardware under categories, that all products in hardware section(all subcategories) such as the mouse,keyboard etc show under that in a products listing..but the will also show when go into a subcategory

 

basically so customers can see a broad product range and go into subcategories as needed