주 (JOO; Real Name:Jeong Min Joo (정민주)) is a Korean singer under JYP Entertainment. She was born on October 11, 1990. She debuted in 2008 with her 1st single, 남자 때문에(Because of A Man). Afterward, she took a two year hiatus and began training. JOO made a comeback in January 2011 with her mini-album Heartmade.