This book provides a comprehensive summary of nanowire research in the past decade, from the nanowire synthesis, characterization, assembly, to the device applications. In particular, the developments of complex/modulated nanowire structures, the assembly of hierarchical nanowire arrays, and the applications in the fields of nanoelectronics, nanophotonics, quantum devices, nano-enabled energy, and nano-bio interfaces, are focused. Moreover, novel nanowire building blocks for the future/emerging nanoscience and nanotechnology are also discussed.