Today we're going to discuss the history of the postal service. In ancient Persia, messengers on horseback carried royal decrees across the empire. However, the system was slow and unreliable, especially in bad weather. It wasn't until the 19th century that the modern postal system emerged, with the introduction of the postage stamp in Britain in 1840. This innovation allowed people to prepay for mail, which greatly increased efficiency. Interestingly, the first stamps were not adhesive; they had to be moistened with water before use.