Engineering light-matter interaction at single quanta level has been a long-standing challenge for realizing optical quantum information technology. One key requirement is to isolate and confine atoms and photons to subwavelength dimensions to realize an efficient quantum interface. In this context, tapered optical fibers with subwavelength diameter waist, optical nanofibers, and nanofiber-based cavities provide a unique fiber-in-line platform for optical quantum interfaces. The key point of the technique is that the fiber-guided light can have strong transverse confinement while interacting with the surrounding medium in the evanescent region. Furthermore, the optical nanofiber-based cavities provide unique possibilities for cavity QED approach to realize an efficient quantum interface. In this seminar, I will discuss the key challenges and experimental developments towards interfacing single quantum emitters to nanofiber-guided modes.