Letter writers will soon be able to express their sentiments in words and smells.The U.S. Postal Service announced Monday that it will issue its first scratch-and-sniff stamps. The stamps feature illustrations of ice pops. The agency says the stamps will "add the sweet scent of summer" to letters.The 20 stamps depict watercolor illustrations by California artist Margaret Berg. Each of the 10 stamp designs includes two different treats. The words "FOREVER" and "USA" appear along the bottom of each stamp.The stamps will be issued on June 20 at a children's museum in Austin, Texas.