The physical organisation, from the molecular to the macro-scale, of essentially all macromolecular materials can profoundly affect the properties and features of the resulting architectures. I will discuss how rules that explain the mechanical properties of the Katana and distinguishes good from lesser tasty chocolates, can be applied to organic semiconductors to manipulate their properties and, hence, and their consequent performance when used as active layers in organic optoelectronic devices, including organic thin-film field-effect transistors, organic light-emitting diodes or organic photovoltaic cells. Here, we present a survey on the principles of structure development from the liquid phase of this interesting and broad class of materials with focus on how to manipulate their phase transformations and solid-state order to tailor and manipulate the final ‘morphology’ towards technological and practical applications. We will discuss blending, nucleation and use of processing aids to control the microstructure targeted for field-effect transistor applications.