Girls' Generation is composed of people.
Girls' Generation . The group is composed of eight members : Taeyeon , Sunny , Tiffany , Hyoyeon , Yuri , Sooyoung , Yoona , and Seohyun . Kim Hyo-yeon ( born September 22 , 1989 ) , better known mononymously as Hyoyeon , is a South Korean singer and television personality .