This book presents and discusses two approaches to studying technological change: the Social Construction of Technology and the Multi Level Perspective. While the account of the approaches is not intended to function as a comparison, an effort was made to structure in a similar manner the presentation layout for each approach in the book. Thus it is possible to look at corresponding sections on key questions, unit of analysis and fundamental concepts in each perspective as well as appreciate their strength in terms of the critique that they have been put to. The book is intended to function as a reference for the reader that is involved in technology studies.