Pinterest has just bought a small start-up called VisualGraph, the company announced yesterday. VisualGraph was started by former Google employee Kevin Ying along with co-founder David Liu, and specializes in search via image recognition. This could be essential to Pinterest's future - as a company that relies on visuals, this technology could add a whole new dynamic to using the social network. With image recognition, Pinterest can introduce an algorithm that will automatically match up photos rather than rely on separate users to pin them together. This potentially massive step forward has already projected a valuation of $4 billion for Pinterest, which just goes to show how important this could be for the social network.