They’ll always be the Summers sisters. Sarah Michelle Gellar and Michelle Trachtenberg became close friends while playing Buffy and Dawn Summers, respectively, on “Buffy the Vampire Slayer” — a tight bond that lasted until Trachtenberg’s tragic death at age 39.

Michelle Trachtenberg’s former “Buffy the Vampire Slayer” costar Sarah Michelle Gellar is looking back at their time together on screen and off, one day after Trachtenberg died in New York City.

Sarah Michelle Gellar is paying tribute to her late "Buffy the Vampire Slayer" co-star Michelle Trachtenberg after her tragic death at age 39.

Sarah Michelle Gellar has paid tribute to her former Buffy The Vampire Slayer co-star Michelle Trachtenberg following her death Wednesday at 39.

Gellar is honoring her late 'Buffy the Vampire Slayer' costar, who died on Wednesday, February 26, with a powerful quote from the show.

Sarah Michelle Gellar mourned the death of “Buffy the Vampire Slayer" co-star Michelle Trachtenberg in an Instagram post.

Nicholas Brendon, Alyson Hannigan, Charisma Carpenter, and others also paid tribute to their former costar after her tragic passing on Feb. 26.

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.

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