Since its foundation 12 years ago, Airbnb has become a mainstay of the tourism industry, and today, is used by an average of two million customers every single night. But the company, which is worth an estimated $35 billion, wasn't an overnight success. In fact, the company took two years to get off the ground, and its biggest early boost came from the founders' decision to sell limited edition cereal boxes. Read on to follow Airbnb's journey from an idea dreamt up in a bedroom in San Francisco, to the multi-billion-dollar powerhouse it is today.