Sarah Michelle Gellar is paying tribute to her late Buffy the Vampire Slayer co-star Michelle Trachtenberg after her death at age 39. Gellar took to Instagram on Thursday to share photos of the pair together on Buffy and throughout their years of friendship.

Sarah Michelle Gellar is paying tribute to her late Buffy the Vampire Slayer co-star Michelle Trachtenberg after her death at age 39.Gellar took to Instagram on Thursday to share photos of the pair together on Buffy and throughout their years of friendship.

Gellar's tribute to her late costar echoes a monologue she delivered in the supernatural drama's season 5 finale.

Fans of Buffy the Vampire Slayer will recognize the caption as a reference to a beloved quote from the show, spoken in the season 5 finale, when Buffy, played by Sarah, sacrifices herself for her sister Dawn, played by Michelle. Sarah's caption also included three heart break emojis and one key emoji—another Buffy reference.

Sarah Michelle Gellar took a walk down memory lane in honor of her late friend and co-star Michelle Trachtenberg.

Sarah Michelle Gellar and Michelle Trachtenberg starred in three seasons of "Buffy the Vampire Slayer" together and remained close following the end of the series.

Fans and friends alike are mourning the loss of Michelle Trachtenberg, who died this week at age 39. Sarah Michelle Gellar was among those sharing tributes to the actor, with whom she co-starred on Buffy The Vampire Slayer.

Several actors, including Blake Lively and Melissa Joan Hart, have paid tribute to Trachtenberg after she died on Wednesday.