From the manufacturer:
Use the magic no-mess pen to trace letters, color in a picture, and see vibrant colors, details, and patterns appear! Each page of the 24-page activity book for kids three and older features safari-themed artwork to complete and seek-and-find activities, too! The invisible ink marker only marks on the pages (not clothing or furniture!) and stores in the cover of the spiral-bound pad, so it's a great travel activity.