Draw & write with light. Reacts to UV light. 2 - 3V batteries included (CR2016). Magic fluorescent UV reactive. Not your ordinary got'a have it out'a this world Lab Putty! No sticky resigoo. Fun never dries out. See back for deets. 1. Watch putty change color as you doodle with UV light. 2. Doodles fade and putty returns to its original color, so the fun never stops. Exputtyment with sunlight & black lights. What else? Mold, knead, bounce, twist, stretch, snap, melt. Conforms to ASTM D-4236. Conforms to the safety requirements of ASTM F963.