 We have developed a model for understanding the molecular orientation disorder in CH3NH3PBI3, which is used to inform the motion of the molecules. The model was based on electronic structure calculations and a Benitio molecular dynamic simulations. It revealed the rich domain structure of twinned molecular dipoles, which varies depending on temperature and applied electric field. This variation can be attributed to the internal electrical fields associated with microscopic polarization domains, which may contribute to hysteresis in the current voltage response of hybrid organic and organic perovskite solar cells. This article was authored by Jarvis M. Frost, Keith T. Butler and Aaron Walsh.