Today's lecture is about the history of the postal service. In the 19th century, the introduction of the postage stamp revolutionized communication. Before stamps, the receiver usually paid for the mail, which often led to refusal. The first stamp, the Penny Black, was issued in Britain in 1840. It featured a portrait of Queen Victoria and cost one penny. This system quickly spread to other countries. However, an important detail is that the Penny Black was only valid for one day, as it was soon replaced by the Penny Red to prevent reuse.