These UV-detecting beads are a real attention getter-driving home the point that this invisible light is a real thing causing real changes. The hole in the ozone layer and the possible damage to living organisms by increased UV radiation has received a lot of study in recent years. These inexpensive beads can be used to help students start their own studies of the effects of UV radiation. These colorful beads turn to various bright colors when exposed to UV light and return to white when stored away from UV light. Have fun designing experiments with these beads. Approximately 240 beads per package.