Which key feature of permanent tissues keeps them in different

Which key feature of permanent tissues keeps them in different category from simple tissues?
Classify these in different types.

After division of cells in both primary and secondary meristems, the newly formed cells become structurally and functionally specialised and loose the ability to divide. Such cells are called permanent or mature cells and form the permanent tissues.
These are of Wo types
(i) Simple tissues (ii) Complex tissues