Confining atoms in hollow-core photonic crystal fibers has opened up new prospects to scale up the distance and time over which atoms can be made to interact with light. Coherent manipulation of external and internal degrees of freedom of guided ultra-cold atoms in optical fibers has been attempted, with the aim of enhancing the performance of quantum experiments and to further develop miniaturized quantum devices. In this talk, I will show our recent works on coupling and guiding cold atoms in a hollow-core photonic crystal fiber and present few key cold-atoms experiments in this hollow-core waveguide environment and discuss their future applications.