Turn on the LED and observe the spectra through prism glasses or diffraction grating film. Drop the waterproof LED into a beaker of water containing dry ice or baking soda and vinegar to observe glowing bubbles in the dark. Use in restaurants to attract service. Originally designed to add to floral displays, they have many uses in the science classroom. Each LED has an on/off switch, will last for over 36 hours and includes two (CR2032) lead-free button batteries.