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Impurity doping is one of the most important techniques to func-tionalize semiconducting nanowires such as silicon and germanium nanowires (SiNWs and GeNWs) for the application to next-generation field effect transistors, sensors, and solar cells. Impurity doping of NWs is generally performed in situ during vapor–liquid–solid (VLS) growth of NWs or ion implantation after growth of NWs. In order to know the status of dopant atoms and to control the impurity doping in NWs, characterization techniques of dopant atoms become more and more important. Naoki Fukata (on pp. 320–330) focused on Raman and electron spin resonance (ESR) to experimentally characterize the bonding states and electrical activities of dopant atoms in addition to scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) methods. Until now, the author has observed local vibrational modes of B (11B and 10B) and P atoms, asymmetric broadening of optical phonon peaks due to the Fano effect, and ESR signal of conduction electrons in NWs, demonstrating that the dopant atoms are located at substitutional site of Si and Ge atoms and electrically activated in them. These are the first observations in SiNWs and GeNWs clearly showing the formation of p-type and n-type SiNWs and GeNWs. The behaviors of dopant atoms were also clarified by using the same characterization method. The characterization methods shown in this paper will be one of the powerful methods to know the status of dopant atoms in nanoscale materials.