The Penny Black is the world's first adhesive postage stamp, issued in the United Kingdom on May 1, 1840. It features a profile of Queen Victoria and was used to prepay the cost of sending letters. The stamp is black in color and has a value of one penny, which is where it gets its name. The introduction of the Penny Black revolutionized postal services by simplifying the process of sending mail. Before its issuance, postage was paid by the recipient, making it difficult for many to send letters. The Penny Black allowed senders to pay in advance, leading to a more efficient postal system.