Without steric control and sufficient flexibility, van-der-Waals interactions result in selfassembly of stacks with strong proximity effect. Mutual shift and twist between the basal planes of the aromatic molecules and intermolecular distance have a strong impact on the resulting electronic structure change, due to the proximity effect. It is possible to control the stacking by strong interlayer interactions, functional groups or steric control units. These control mechanisms are still beyond the state -of-the-art and subject of the authors' ongoing research efforts.