Social has gone visual. That’s the best way to sum up the new data coming out of Hitwise UK this week that shows how two niche activities a year ago – snapping photos on the go and sharing them with your network  and pinning pics of fashions and recipes and cutting-edge design – has become a global phenomenon.

Instagram and Pinterest are by far the fastest-growing social networks on a global scale. Instagram has grown over 2,000% in the last year in the UK and over 17,000% in North America. No wonder Facebook paid a cool billion in cash for it a few months ago. Pinterest is showing similarly impressive growth figures. Here’s the growth story in chart form:

Instagram, which just topped the 80 million user mark, is likely to continue to see its impressive growth streak continue for some time as its popularity rises alongside the growth of smartphones. Pinterest is less harder to gauge. Its scrapbook style social networking means it is enormously popular with females and collectors. But Pinterest does face competition from a dizzying number of copy-cat rivals, and, it’s yet to figure out how to monetize its user base of more than 20 million. And, just this week, further doubts have been cast upon its ability to drive meaningful traffic downstream.

Still, the success of the past year for Pinterest and Instagram points to one enduring truth: the power of the visual social networks in building a global, loyal and active following. We already saw the appeal of Instagram to Zuckerberg & Co. It will be interesting to see how brands can exploit this phenomenon as well.