Girls' Generation includes Hyoyeon.
Girls' Generation . The group is composed of eight members : Taeyeon , Sunny , Tiffany , Hyoyeon , Yuri , Sooyoung , Yoona , and Seohyun . Kim Hyo-yeon . 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 .