Subcategories (Tasks/CRM/Projects)??

Subcategories (Tasks/CRM/Projects)??

Hi, 

I really love your product because it combines tasks and email in a nice way.
Even dough, I am trying to create a task list with subcategories and can't make it, no matter where I try!
No subcategories in Tasks, no subcategories in CRM, no subcategories in Projects.

Am I missing it or wrong? I think this most be an option and I am not the first who's asking for it.

Many thanks