Wired: Instagram has been tiptoeing into the world of mobile advertising since 2013, wary of upsetting its 300 million users. But now, Instagram has announced a major change with the introduction of slideshow ads. The new ad format, which the company calls “carousel,” will allow advertisers to post several photos at once for users to flick through. But perhaps more critically, these ads will also let advertisers link to external websites where users can learn more about their brands.