Dr. Nicole B. Ellison has been a pioneer in research on social network sites (SNSs). Her 2007 and 2013 articles on SNSs (with Dr. danah boyd) have over 17,000 citations. In this dialogue, Dr. Ellison looks back and shares the backgrounds of her first study on SNSs. She then discusses whether a new definition of SNSs is needed as the platforms have changed so rapidly. She also provides insights into the challenges and opportunities for future research on SNSs.