Photo luminescent crystals generate a glowing effect; the more crystals the longer and brighter the glow. Heavenly Horses Alight the Night(TM) are carefully created with twice the amount of crystals than standard glow products, which causes them to glow all night. For best results expose your horses to strong light for 5 to 10 minutes, then enjoy your equine friends all night while they gradually fade, delighting every horse-loving spirit.Photo-luminescent material is used by NASA as a secondary light source. Our 4" peel n' stick collectibles