Claim: Girls' Generation includes Hyoyeon.
Evidence: The group is composed of eight members : Taeyeon , Sunny , Tiffany , Hyoyeon , Yuri , Sooyoung , Yoona , and Seohyun.
She debuted as a member of girl group Girls ' Generation in August 2007 , who went on to be one of the best-selling artists in South Korea and one of South Korea 's most popular girl groups worldwide.