The introduction of an ambient-temperature route for integrating high-mobility semiconductors on flexible substrates could enable the development of novel electronic and photonic devices with the potential to impact a broad spectrum of applications. Here we review our recent studies demonstrating that high-quality single-crystal nanowires (NWs) can be assembled onto flexible plastic substrates under ambient conditions to create FETs and light-emitting diodes. We also show that polymer substrates can be patterned through the use of a room temperature nanoimprint lithography technique for the general fabrication of hundred-nanometer scale features, which can be hierarchically patterned to the millimeter scale and integrated with semiconductor NWs to make high-performance FETs. The key to our approach is the separation of the high-temperature synthesis of single-crystal NWs from room temperature solution-based assembly, thus enabling fabrication of single-crystal devices on virtually any substrate. Silicon NW FETs on plastic substrates display mobilities of 200 cm/sup 2/-V/sup -1/-s/sup -1/, rivaling those of single-crystal silicon and exceeding those of state-of-the-art amorphous silicon and organic transistors currently used for flexible electronics. Furthermore, the generality of this bottom-up assembly approach suggests the integration of diverse nanoscale building blocks on a variety of substrates, potentially enabling far-reaching advances in lightweight display, mobile computing, and information storage applications.