leader of the group is  Kim Taeyeon . The other members are  Jessica Jung ,  Lee Soon Kyu  (Sunny),  Stephanie Hwang  (Tiffany),  Kim Hyoyeon ,  Kwon Yuri ,  Choi Sooyoung ,  Im Yoona  and  Seo Joo Hyun .              1 . Career 1.1 2007–2008: Debut and Girls' Generation