The performance of organic electronic devices, such as solar cells, depends on understanding and controlling the solid-state microstructure of semiconducting polymers. In this talk, I will discuss on our recent understanding of the aggregate states, solid-state microstructure, and thermotropic behavior of the best-performing family of polymers for solar cells, i.e., benzodithiophene-based semiconducting polymers. I will argue that the microstructure of these polymers does not seem to fit neither in the traditional structural models developed for polymers, i.e. the amorphous and semi-crystalline models, nor with other stablished low-order structures, a.k.a. solid mesophases, such as condis crystals, liquid crystals, hexagonal phases, columnar phases, paracrystals, and so on. Conversely, these polymers organize into a unique solid mesophase that resembles sanidic structures while also sharing features with columnar mesophases like condis-crystals. Interestingly, structural order along crystallographic directions seem to be decupled in these staructures. At a larger length-scale, the mesophase organizes into nanoscale fibril-like domains, with polymer backbones aligned along the fibril axis, coexisting with amorphous-like glassy regions. I will also discuss on the thermotropic behavior of this biphasic nanomorphology, providing insights into how thermal annealing influences polymer structure. Finally, relevant interconnections between processing, microstructure and mechanical properties will be discussed.The understanding of the structure of semiconducting polymers enables a more precise framework for defining structure-function relationships, impact thus on the entire field of organic electronics, from organic photovoltaics to bioelectronics to wearable electronics