Social networks that appeal to women are written off as silly time-wasters (see: Pinterest), and ones that appeal to young girls are taken even less seriously. That's how 7-year-old We Heart It has flown under the radar for all this time, despite amassing millions of users and several high-profile advertisers.

Like Pinterest, We Heart It is an online bulletin board that allows you to collect and share inspirational images. The two diverge when it comes to audience. For some reason, We Heart It has captured the attention of teen girls, who love posting collections of vintage fashion, body art, and funny sayings--and brands are paying attention. Companies like Hollister, Old Navy, and Vera Wang have signed up to run ads on the platform. YouTube chose We Heart It to test an early run of its new creators campaign.

Brazilian designer Fabio Giolito started We Heart It as a design inspiration site in late 2007 as something of a side project for other designers to contribute to. It wasn't until 2011 that Giolito, seeing the success of rival Pinterest, decided to turn We Heart It into a legit business.

A bully-free space

Now the network has nearly 30 million users and adds about a million every month. About 80 percent of We Heart It's users are under 24, and its iOS and Android apps draw 80 percent of the network's traffic. The network is warm and fuzzy, filled with artistic shots of donuts and beachy landscapes. It's for kids who know Lauren Conrad from her Instagram feed and not her fine work on MTV's Laguna Beach (her reality series before The Hills). No wonder Hollister's on board.

Plenty of apps are popular with teens – Snapchat, Whisper, Instagram, and the like – but We Heart It is aiming to be a little less stressful than those networks.

"We wanted to keep We Heart It all about inspiration and ideas, sharing things in a positive way," said We Heart It president Dave Williams. "For both of those reasons we made a decision not to have any kind of commenting. It keeps the platform very positive. There's no way for users to tear each other down."

You can follow another person's collection or heart the image, but you can't say anything negative – which is probably another reason why advertisers are hopping on board. There's also none of the insane "follow me pleeeeeeeeease" type of behaviour commonly seen across Instagram.

"The pressure to compete is another big thing," Dave said. "We do encourage people to follow one another but we don't celebrate overtly the number of followers you have versus someone else."

The network's next step

We Heart It is still in the early days of its advertising experiment. Like other free networks, it's trying to place unobtrusive, native ads in its stream without upsetting users. Ads appear as images in the network's trending feed and look just like any other post. Instead of a user sharing an inspirational Nike slogan, Nike can advertise itself, and no one will really know the difference.

That's how We Heart It ads will differ from Pinterest's model, Dave said.

"TV advertising is designed around creating an emotional connection to a brand," he said. "Internet advertising has not really been brand-oriented as much, it's been about that click-through. We think that's a model that can work, but we're really about the idea. We're more focused on which brands resonate with [users], rather than which shoes they're going to buy right now. We're more like a glossy magazine than a catalog."

We Heart It is exploring ways to let you create your own mini magazines on the network with Collections, which are similar to Pinterest's themed boards, and plans to continue in that vein.

"Collections have become almost like playlists," Dave said. "I'm an amateur photographer, but I can certainly make a collection that resonates, in the same way that I can't create a top 40 song, but I can create a playlist that expresses who I am."

A safe space for teen girls to express themselves without hearing any negative feedback from their peers sounds like a relief for parents – even if the rest of the Internet is blissfully unaware that such a place exists.