Advertising has existed in various forms for thousands of years. Early forms included stenciled brick advertisements from Babylon, town criers in medieval times, and painted signs in ancient Rome and Egypt. The printing press was a major development, allowing mass production of flyers and posters. In the 19th century, the growth of newspapers, railroads, and telegraph networks facilitated nationwide advertising. The development of radio in the 1920s and television in the 1950s further expanded advertising's reach into consumers' lives. Advertising has become more scientific over time through audience research and testing to evaluate effectiveness.