It's a Costume Institute Gala and it is the fashion industry big night. People and celebrities come dressed to impress.
So scroll down for some glitz and glamour.
Carey Mulligan in Prada, she looks like she just stepped off a glam sci-fi movie
Jessica Alba in Michael Kors, gold Grecian gown, a tad too much I think or I've seen it before.
Beyonce in Givenchy in the dress that everybody is talking about. Figure-hugging, flesh-coloured fabric and a purple tail. A mermaid and spiderwoman mixed in one.
Diane Kruger in Prada. On the theme of purple tail, this one has feathers on it. What do you think, do they feathers look good?
Alexa Chung in Marc Jacobs, she is just a little underdressed compared to everyone else. Quirky but not so dress appropriate for this big event.
Leighton in Marchesa, Queen B in an overwhelming dress. Her hair almost matches the colour of the dress.
Christina Ricci in Thakoon. She is in a bold dress. The bow is a big statement, the fan in the front is a big statement. I know this might be too much for some, but I LOVE this dress. Soft pastels with some sparkles and black. Love it.