*NSYNC got back together, but only to celebrate a major birthday for one of its members.
All five members of the popular boyband came out in support of bandmate JC Chasez's 40th birthday party Monday night -- and even posed for a group photo.
"JC's 40th... And, if you don't know now you know..." Justin Timberlake posted alongside an Instagram shot of the whole group -- including Chasez, Chris Kirkpatrick, Lance Bass and Joey Fatone.
Chasez posted the same image to his own Instagram along with the caption, "So many feels".
If Chasez turning 40 isn't enough to make you feel old, consider this: The group's final album together, "Celebrity," was released 14 years ago.