MPK, a company that has made a name producing glow-in-the-dark paint, has developed self-luminous micro particles called Litrospheres. The new material is said to be inexpensive (35 cents to light up a 8 ½ x 11 piece of plastic that is 1/8" thick), non-toxic, and capable of staying constantly lit for over 12 years thanks to a betavoltaic technology that uses a radioactive gas.
Fortunately, the gas is involves a "soft" emission of electrons that cannot penetrate the glass or polymer wall of the microspheres. So theoretically, you don't have to worry about brain tumors or taking on super powers when using it.
The Litrospheres, which can be injected molded or added to paint, are not affected by the heat or cold and they can withstand up to 5000 pounds of pressure. They can also give off light that is equivalent of a 20-watt incandescent bulb in almost any color imaginable. As you might expect, the first applications of the technology will most likely involve safety equipment—or the clothing and accessories of frequent clubgoers. [Wiki via Treehugger]