Iterative Protocols is thought as an introduction to generative design through Processing, Open-source programming environment supported by GNU/Linux, Mac OSX and Window operating systems. The aim is to provide a comprehension of non linear systems and how complexity can emerge from very simple initial rules. We will scrutinize how, through OOP paradigm it is possible to access and generate an aesthetic (as morphology and communication) of emergent complexity through the coordinated interaction of simple rulesets. Starting from basic interacting geometric elements up to Cellular Automata and agent systems.