Nanosystems are large-scale integrated systems exploiting nanoelectronic devices. In this work, we consider double independent gate, vertically-stacked nanowire FETs with gate-all-around structures and typical diameter of 20-nm. These devices, which we have successfully fabricated and evaluated, control the ambipolar behavior of the nanostructure by selectively enabling one type of carriers. These transistors work as switches with electrically-programmable polarity and thus realize an exclusive or operation. The intrinsic higher expressive power of these FETs, as compared to standard CMOS, enables us to realize more efficient library cells, which we organize as tiles to realize circuits by regular arrays. This article surveys both the technology for double independent gate FETs as well as physical and logic design tools to realize digital systems with this fabrication technology.