The experiment carried by the author in 2010 is to test if self-organizing systems could be systematically regulated according to the user’s preference for global behavior. Self-organizing has been appreciated by architects and urban planners for its richness in the emerging global behaviors; however, design and self-organizing are contradictory in principle. It seems that it is inevitable to balance the design and self-organization if self-organization is employed in a design task. There have been approaches combining self-organizing with optimization process in a parallel manner. This experiment strives to regulate a self-organizing system according to non-defined objectives via real-time interaction between the user and the computer. Particularly, cellular automaton is employed as the self-organizing system to model a city district.