Bol.com started as a Dutch online bookstore in 1999 and has since grown to become the largest online retailer in the Netherlands, serving over 6.6 million customers through its website and mobile apps. The document summarizes Bol.com's journey and key learnings from expanding into new product categories and platforms like its marketplace (Plaza), which started with second-hand books and has grown exponentially. Bol.com has also learned the importance of social features, customer reviews, recommendations, and enabling third-party sellers on its marketplace to provide the best shopping experience for customers.