Over the past decades, glass-ceramics doped with transition metals have become promising materials for the development of active and passive optical functional devices, interesting a wide variety of commercial applications due to their unique properties. In this Perspective paper, the intrinsic advantages of these composite materials are outlined and we provide an overview of recent and ongoing progress and state-of-the-art knowledges of the main applications: broadband amplifiers, tunable lasers, long persistent phosphors, non-invasive optical temperature sensors, saturable absorbers, high IR emitters and thermal shock-resistant color filters. Finally, the today challenges and future prospects are exposed to provide guidelines for future research.