User-centered design has been widely practiced by user experience (UX) professionals for many years, and a variety of methods have been used to facilitate UCD practices (Nielsen, 1993; see Chapter X of this book). UX professionals herein refers to the people who are practicing UCD, including human factors engineers, UX designers, human-computer interaction (HCI) specialists, usability specialists, and the like. The philosophy of UCD places emphasis on the end users when developing usable products (e.g., applications, services). It focuses on users by understanding the users, learning their environments and contexts of their usages, and realizing their needs in usable products.