From gold dust to microchips. How Silicon Valley became the cradle of innovation. What started as a wild frontier during the Gold Rush turned into the home of world-changing inventions. And its story still matters to every founder building something new today.

Many great businesses started as small, part-time projects. Let's look today at the 10 successful startups that started as side projects (GitHub, Trello, Gmail, Craigslist, Twitter, Angry Birds, Instagram, Product Hunt, Unsplash, GrowthHackers).