Among various nanostructures for low-dimensional photonics, the one-dimensional nanowire is of great importance owing to its capability of routing tightly confined light fields in single-mode with least space and material requirement, minimized optical path, and high mechanical flexibility. Free-standing optical nanowires or nanofibers fabricated by either chemical growth or physical drawing techniques surpass nanowaveguides fabricated by almost all other means in terms of sidewall smoothness and diameter uniformity, conveying their low waveguiding losses.With high index contrast between the core and the surrounding, a nanowire can guide light with tightly confined large fractional evanescent waves, which enables highly localized near-field interaction between the guided fields and the surrounding media. In this talk, we show the possibility of on-chip integration of free-standing optical nanofibers and nanowires. Firstly, by embedding nanofibers with microfluidic chips, we show ultrasensitive optical sensors for physical and bio-chemical detection. Secondly, by near-field coupling of free-standing nanowires/nanofibers with silicon-on-insulator waveguides, we show hybrid photonic circuits for optical modulation and light generation on silicon chips.