Collections suggestion: Nested Collections

I can see a use for the ability to have collections inside of collections.

First one that comes to mind is recipes. 

└───Recipes
    └───Beef
        ├───Stew
        │   ├───RecipeSite1
        │   └───RecipeSite2
        └───Crockpot
            ├───RecipeSite3
            └───RecipeSite4

Tags could possibly satisfy this as well.