Instagram is now offering brands a new way to sell-on-Instagram through ad unit that enables shopping as the site moves further into the e-commerce space.

The photo- and video-sharing app – owned by Facebook – started testing ads that blend videos and product catalogs where consumers can complete purchases without leaving. Instagram calls them “collection” campaigns.

The function was first tested on Facebook, which uses its different properties as testing grounds before expanding ads and services across the platform.

E-commerce is continuously becoming a big opportunity on Instagram, and a competitive category in its rivalry with Snapchat. Both platforms offer features to brands that link to purchases outside the apps, and both are slowly bringing the power to purchase inside the apps.

Fashion and beauty brands Birchbox and Revolve are the first marketers to try “collection” ads on Instagram. There are 200 million people following fashion-related accounts on Instagram, according to an Instagram spokeswoman.

Instagram, meanwhile, is becoming an important driver for the future of Facebook’s business. Last week, Facebook’s earnings report showed that the number of people on the social network had declined in North America for the first time and that people were even spending less time on the platform.

Facebook has more than 5 million advertisers, while Instagram has around 2 million. There are 70 million businesses on Facebook and 25 million on Instagram making it a  good to sell-on-Instagram.

Facebook wants to give more advertisers the ability to easily extend campaigns from one platform to the next, and drive more of the advertisers to all its properties.

“Instagram is a business’s visual shop on mobile, and we’re seeing more people seek out businesses there,” said Sheryl Sandberg, Facebook’s chief operating officer, during the earnings call with analysts last week. “About two-thirds of the visits to Instagram business profiles are from people who don’t yet follow them. This is how many businesses are finding new customers.”