In recent years organic photovoltaics have become one of the most increasing research areas due to their potential towards a cheap and broad applicability. Besides the chemical structure and the resulting electronic and absorption properties, the morphology of the active layer in such systems was found to be one of the most important issues to gain reasonable device performance. The development of tomography and advanced scattering techniques enables the detection of 3-dimensional morphologies in these materials. In this review we focus on the latest findings concerning the morphology and its control parameters in
