We show that locally altering fused silica with femtosecond laser irradiation forms the basis for a novel manufacturing technology platform to produce highly integrated microsystems. In contrast to many common approaches that rely on combining materials to achieve particular functions, our scheme utilizes a single piece of material, whose properties are locally modified using femtosecond laser irradiation. This microsystem fabrication method is not only particularly attractive for optofluidics instruments but also for optomechanical devices.