It's basically the best thing that could ever grace our screens.
WATCH: Harry Styles continues to showcase his killer dance moves with Milly Bobby Brown at Ariana Grande's concert
Millie attended the concert with co-stars from her new film Enola Holmes.
She has been a big Ariana fan for a long time.
As for Harry - he has actually worked with Ariana before, writing her beautiful song "Just A Little Bit Of Your Heart", that he also performed on his own world tour recently.
This is a GOOD day. Thank you world.
