It’s not an easy task to figure out the gifts to buy your kids that will have them jumping for joy Christmas morning. Some kids put every gift imaginable on their wish lists, while others change their minds almost daily. And then there are kids who will only tell Santa what they want.

For parents who face that challenge, Jonna Mendez — former CIA Chief of Disguise and our Target Kids’ Gift Detective — has a tip to help extract the intel you need for your covert Christmas shopping mission — and create a fun family activity as well.

Ask your kids to make a wish list for Santa with special, “invisible” ink that only the big guy can read. Here’s your how-to guide to creating the concoction at home — it’s as easy as 1, 2, 3. Literally.

What You’ll Need:

  • Lemon juice or milk
  • Glass Mason jar or other festive container
  • Label and pen
  • Hair Dryer

Infographic: Decoding Letters to Santa