There are few applications available in the community to help teenagers manage pain after surgery. The focus of this study is to better understand the pain experience of children after having surgery and to design a Smartphone app called iCanCope with Post-Operative Pain (iCanCope PostOp), to help children and parents to better manage pain at home after surgery. The app will help keep track of pain, provide information about the teenager's surgery and provides in-the-moment advice wherever and whenever the patient needs it.