|Root Category 1 > Sub-Category 1 > Sub Sub-Category 1|
|Helmets > Street Helmets > Full Face Helmets|
|Helmets > Street Helmets > Open Face Helmets|
This is typically how a category hierarchy would look, it is important to layout a good strategy for your categories before creating too many. Often times you will find that you will need to make changes along the way so you want to plan as far ahead as possible.