Lady Gaga delivered a powerful performance during the 88th annual Academy Awards on Sunday as she took the stage at the Dolby Theater to sing her song "Til It Happens To You," the Oscar-nominated song that the pop star co-wrote with Diane Warren for the campus sexual assault documentary, director Kirby Dick's 2015 film "The Hunting Ground."

The 29-year-old pop star was introduced by Vice President Joe Biden, who urged the audience to pledge to take a stand against sexual assault on college campuses and introduced the "Bad Romance" singer as his "friend" and "a courageous lady." She then took the stage dressed in white and sat behind a white grand piano to perform her song.

Joining her onstage were 50 survivors of sexual assault, including some of the survivors who were featured in "The Hunting Ground." Gaga herself is also a survivor of sexual assault, and she has spoken out about her own experience in the past, but there are two very important women in her life who didn't know about her assault - her grandmother Ronnie and her aunt Sheri. Gaga posted a photo of her grandmother and her aunt on Instagram and shared their emotional reactions to learning about the assault she endured.

"My grandmother (in the middle) and my Aunt Sheri (on the right) both called me the day after the Oscars because I never told them I was a survivor," Gaga wrote in the caption. "I was too ashamed. Too afraid. And it took me a long time to even admit it to myself because I'm Catholic and I knew it was evil but I thought it was my fault. I thought it was my fault for ten years."

"The morning after the Oscars when I talked to my grandmother Ronnie, with tears in her eyes I could hear them welling through the phone she said to me, 'My darling granddaughter, I've never been more proud of you than I am today,'" she continued. "Something I have kept a secret for so long that I was more ashamed of than anything-- became the thing the women in my life were the most proud of. And not just any women, the ones I look up to the most. #BeBrave #speakup #tilithappenstoyou"

See Gaga's Instagram post below.

 My grandmother (in the middle) and my Aunt Sheri (on the right) both called me the day after the Oscars because I never told them I was a survivor. I was too ashamed. Too afraid. And it took me a long time to even admit it to myself because I'm Catholic and I knew it was evil but I thought it was my fault. I thought it was my fault for ten years. The morning after the Oscars when I talked to my grandmother Ronnie, with tears in her eyes I could hear them welling through the phone she said to me "My darling granddaughter, I've never been more proud of you than I am today." Something I have kept a secret for so long that I was more ashamed of than anything-- became the thing the women in my life were the most proud of. And not just any women, the ones I look up to the most. #BeBrave #speakup #tilithappenstoyou

A photo posted by Lady Gaga (@ladygaga) on Mar 1, 2016 at 5:04pm PST