Although start-ups represent a major phenomenon in the USA, they also create skepticism and even suspicion, perhaps because of the excesses of the Internet bubble. Apple, Microsoft, Intel, Cisco, Yahoo and Google were all start-ups and these success stories show that the phenomenon is not mere speculation. The goal of this book is to show start-ups from a different angle. Start-ups are created by individuals who are passionate and who have dreams. Therefore this work should not only be read by specialists of innovation or by high tech entrepreneurs, but also by anyone interested in the history and economics of start-ups. The book is presented in two parts: it begins with a presentation of Silicon Valley start-ups, which ends with a description of the ecosystem of this region. The second part is dedicated to Europe, where the start-up phenomenon has failed in comparison. The main message is that it is absolutely necessary to take more inspiration from Silicon Valley.