The development of multimaterial and multifunctional optical fibers is opening exciting opportunities in photonic and optoelectronic devices, optical probes, diagnosis and surgical tools, as well as advanced fibers and textiles. It also constitutes a rich platform for the fundamental study of novel materials science and processing concepts, as well as in optics and photonics. This Feature Issue is a collection of thirteen peer-reviewed articles that present original work in areas at the frontier of this emerging scientific and technological field. These contributions highlight the maturity of the techniques employed to date, their potential to further develop and the prospects for a new generation of optical fiber based devices. (C) 2017 Optical Society of America