2016: Debut with "The 7th Sense" and "Without You"
On April 4, NCT U was announced with pictures announcing members Mark and Jaehyun, later adding members Taeil, Taeyong, Doyoung, and Ten. NCT U was described as the main group of NCT. It was announced that there will be two NCT U groups, each having different member organization. On April 9, they released the song "The 7th Sense" and "Without You" as digital singles, Jaehyun, Mark, Ten, Taeyong, and Doyoung participated in producing "The 7th Sense" which is described as having a hip-hop groove with a heavy base sound. As for “Without You,” members Taeil, Jaehyun, and Doyoung worked to create the dance EDM song. The group made their debut on music program Music Bank four days later.
2018: "Timeless" and NCT 2018
On January 12, NCT U released the single "Timeless" as part of STATION 2 and featured members Taeil, Doyoung, and Jaehyun.
On March 14, the NCT 2018 album NCT 2018 Empathy was released and gave the unit three new songs, as well as new members, such as "Boss," "Yestoday," and "Baby Don't Stop." The "Boss" lineup consisted of Taeyong, Doyoung, Jaehyun, Winwin, Jungwoo, Lucas, and Mark. Meanwhile, the "Baby Don't Stop" lineup consists of Taeyong and Ten. The "Yestoday" lineup consisted of Taeyong, Doyoung, Lucas, and Mark.
2019: "STATION X 4 LOVEs for Winter Part.2"
On December 13, NCT U released the single "STATION X 4 LOVEs for Winter Part.2" as part of STATION X. The single which includes the song "Coming Home" featured Taeil, Doyoung, Jaehyun, and Haechan, latter of whom making his debut in the unit.