1. Advertising has historically developed from early signs and town criers announcing products, to the invention of printing allowing mass printed advertisements in newspapers and magazines.
2. Radio advertising emerged in the 1920s, with the first paid radio commercial in 1922, and sponsorship of whole radio programs growing in popularity in the 1940s.
3. Television became a revolutionary new advertising medium in the 1940s, being the first audio-visual format and allowing advertisers to reach mass audiences.
4. Online advertising began in the 1990s with banner ads, and has since grown exponentially through social media, emails and other digital formats, allowing advertisers to easily reach broad global audiences.