Abstract: This invention relates to a means for more efficiently and more safely providing self-luminous lighting devices for use in signs, markers, indicators and the like. Said invention provides self luminosity by means of a plurality of glass microspheres containing both a light emitting phosphor and a radioactive gas. The "soft" emission of electrons from the beta emitting gas can not penetrate the glass wall of the microspheres, thereby constituting no radiation hazard. The containment of the self-luminous system within an envelope which does not pass any radiation prevents the deterioration of nearby organic materials. A further advantage of said invention is that the plurality of individual containment envelopes minimize the escape of radioactive gas in the event of any physical damage to an assembly of such envelopes. A still further advantage of my invention is that the radioactive gas completely surrounds the phosphor particles, thus causing light emission from 100 percent of the surface of said particles.