This Necklace Is Great For Parties Or Any Indoor Or Outdoor Night-time Event. Charm Needs To Be Charged In Uv Light Before It Can Glow -- Sunlight And Black Light Will Produce The Longest, Brightest Glows. Just A Few Minutes Of Charge Can Produce A Glow That Lasts For Hours! Glow Is Brightest Immediately Upon Entering Darkness And Gradually Fades To A Soft Hum Over The Hours Until Item Is Recharged. Can Be Recharged Over And Over For Enjoyment!