This fine point marker, is loaded with special ink that is only visible under UV light. It includes a mini LED UV black light with batteries, so you can view your messages. Children think that they are secret agents with these pens, lay mystery adventures and writing clues for each other. You can make secret messages with your friends. Perfect theme for a fun party favor, for drawing, secret message writing, currency checking, security marking. It is a great gift for your lover, family and friend. Remove the cap Our Invisible Ink Pen comes with full invisible ink, once the cap is removed, the marker is ready to be used. Make sure to place the cap back on after finished writing your message. Write your secret message You will not be able to see the message, but it is there! Write as you normally would, but if you need guidelines, use the UV light to continue! You can write in ANY surface. Turn the UV light to reveal message The UV light is located on the cap of the pen, and it comes with batteries included, switch the button on/off and reveal your secret messages with ease. HeroFiber Invisible ink pens 1. Write down secret information with a pen. Don't worry about being discovered 2. This non toxic and tasteless ink is a safe toy for children 3. Can be used on fabric (T-shirts), paper, skin, or any smooth surface, permanent ink but washable! 4. Children love these spy pen kits 5. Use this pen to keep secrets and play detective games 6. Perfect gift for children at parties, school, giveaways, or other events