Infinite subcategories

Hi All, Time ago, somebody sent a sample to the list about how to do an "infinite" subcategories, based on parent field. I´ve been googling, and searching my mail history, but cannot find it..... The objective is to create a tree with categories and subcategories of documents, but with no limit into the subcategory depth. Anybody remember that thread, or can point me to a solution? Thank you Regards -- dpc