The way I understand it is applying Chomsky grammar rules (eg. A -> ABF; B -> CFF) but in singular passes rather than expanding to its full length. Eg:
By drawing/considering these iterations you can model cell/biological growth over time; applying the grammar in its whole immediately would only get you to the end result, plus would never end if you had fractal/infinite sequences.
Let --- A -> BFC B -> CF+ C -> F-
0. ABC 1. BFCCF+F- 2. CF+FF-F-F+F- 3. F-F+FF-F-F+F-
By drawing/considering these iterations you can model cell/biological growth over time; applying the grammar in its whole immediately would only get you to the end result, plus would never end if you had fractal/infinite sequences.