Exo-cbx (hangul: 엑소-첸백시; stylized as exo-cbx , also known as cbx or chenbaekxi ) is the first official sub-unit of south korean boy group exo. formed by s.m. entertainment in 2016, the group is composed of three exo members: chen , baekhyun , and xiumin . their debut extended play hey mama! was released in october 31, 2016.