Group Categories tree - IMPORTANT

Hi there,

is anybody know how to make in group categories a tree - subcategories?

I need very useful solution:

Main category 01
- subcategory 01
- subcategory 02
- subcategory 03

Main category 02
- subcategory 01
- subcategory 02
- subcategory 03

etc.

Is anybody know how to do this?
This is very useful and must have in ES, so how to achieve this? :-)


Thank you and regards!
Adam