Organic electronics is a technology enabling the fabrication of mechanically flexible/stretchable electronic circuits and devices using low-temperature, possibly additive, processing methodologies. In this presentation we report the development of novel materials, as well as thin-film engineering, for flexible and stretchable organic and inorganic thin film transistors and circuits. In particular we show that “ultra-soft” polymers can be synthesized by co-polymerizing naphthalenediimide (NDI) or diketopyrrolopyrrole (DPP) units with proper co-monomer building blocks and by NDI/DPP core substitution with hydrophylic/hydrophobic substituent. On material development we also report fabrication of stretchable inorganic metal oxide fiber network using spry coating. Furthermore, we discuss new “soft” transistor architectures using semiconductor film porosity as key element enhancing mechanical flexibility and tune charge transport which, combined with elastomeric pre-stretching, enables unprecedentedly stable current-output characteristic upon mechanical deformation. Finally, we demonstrate integration of these devices for sensing analytes, strain, light, temperature and physiological parameters.