On Sunday night Ariana Grande held a star-studded benefit concert called One Love Manchester. It was organised to help raise funds for the victims and families affected by the bombing at her concert in the city on 22 May.
Everyone from Coldplay to Miley Cyrus, Justin Bieber, Take That, Little Mix, and Liam Gallagher performed.
And one of the star performers of the night was Katy Perry.
Katy told the crowd: "It's not easy to always choose love, is it? Especially in moments like these. It can be the most difficult thing to do. But love conquers fear and love conquers hate. And that love that you choose will give you strength."
She then sang her tracks "Part of Me" and "Roar" as she appeared onstage in a long, white, furry coat.
But when she took off her coat, this dress was revealed with a touching detail.
It was made out of pictures of the 22 victims who sadly lost their lives when terrorists targeted Ariana's concert in Manchester last month.