Get ready for your mailbox to smell a little sweeter — this summer, the U.S. Postal Service will introduce its first-ever scratch-and-sniff stamps. The Forever stamps will be sold in booklets of 20, featuring 10 watercolor illustrations of popsicles designed by artist Margaret Berg of California. The stamps will be issued on June 20, with a dedication ceremony at the Thinkery Children's Museum in Austin. The exact scent remains a mystery, and won't be revealed until next month, but the Postal Service did issue a few clues in its press release: "In recent years, frozen treats containing fresh fruit such as kiwi, watermelon, blueberries, oranges, and strawberries have become more common.