Photonic crystal fibers exhibit physical features, from various angles, more versatile, intriguing and promising than those pertaining to the conventional optical fibers. Their cross-section can be optimized to obtain single mode operation on a wide wavelength range, soliton propagation, regeneration application, controllable group velocity dispersion. Moreover their core can be rare-earth doped so obtaining high-performance optical amplifiers and lasers or active components for optical communication systems. A few, non exhaustive, examples illustrating the state of the art of photonic crystal fibers are here reported.