l         With this incredible pen, write with invisible ink and use the special, attached ultraviolet light at the other end to read the message. The pen's UV light causes the ink to fluoresce in the visible region. The use of such a pen was part of the plot in The Da Vinci Code by Dan Brown. Use this pen to mark unknown samples for students in the laboratory. This new product is sure to become one of our most popular... everyone we've showed it to, wants one!