when This is Us" star just shared a very '90 with Justin Timberlake, when she was opening up for NSYNC.

At the time, the 15-year-old (15!) had a hit with her single "Candy." She later had hits with 2000's "I Wanna Be With You" and 2001's "In My Pocket." She's still singing as Rebecca on the NBC series "This is Us."

On her Instagram post, she wrote: "Summer of 1999. Abercrombie tshirts and bucket hats. Opening for this guy and his band. Look at my nervous smile! ???? #tbt #memories"

And as for what her "This is Us" hubby Rachael Leigh Cook's house.