Communication: The fabrication of a laser based on mesoporous fibers is shown to be possible, demonstrating for the first time that mesostructural systems can be applied as advanced optical materials. The amplification of a guided mode in the fiber and the resulting, gain-narrowed emission (illustrated on the cover of this issue) are reported. It is stressed that the system used-a composite containing the dye rhodamine 6G-is a relatively simple type of laser material and better results can be expected in thp future with different types of lasing guests in mesoporous fibers.