1. Jessica Simpson shared this photo of when she did a shoot for Allure magazine in 2006. Instagram: @jessicasimpson 2. Iman posted these photos of when she and Madonna attended an AIDS benefit for New York's St. Vincent’s Hospital in 1986. Instagram: @the_real_iman 3. Dan Levy shared this cute photo of himself from the mid-'80s. Instagram: @instadanjlevy 4. Joseph Gordon-Levitt kept the cute theme going and posted this photo of him and his cat in the early '90s. Instagram: @hitrecordjoe 5. Rashida Jones shared this photo she and her friends took at the mall in the early '90s. Instagram: @rashidajones 6. In honor of her friend and Buffy co-star Seth Green's birthday, Sarah Michelle Gellar posted this childhood photo of the two of them in the early '80s. Instagram: @sarahmgellar 7. Mark Ruffalo posted this photo of himself taken in the early '90s, when he was a struggling actor in LA. Instagram: @markruffalo 8. Paul McCartney shared this photo his late wife, Linda McCartney, took of him in the bath in 1969. Instagram: @paulmccartney 9. U2 celebrated the 21st anniversary of their album Pop by posting a clip from the lead single, "Discothèque." Instagram: @u2 10. Barbra Streisand posted this photo from the ’60s of herself in the kitchen of her first home alongside her beloved dog, Sadie. Instagram: @barbrastreisand 11. Will Smith shared this clip of himself talking about his memories of the first time hanging out with the legendary group Run-DMC. Instagram: @willsmith 12. And finally, Kelsey Grammer shared this touching tribute to his Frasier co-star, John Mahoney, who died earlier this week.