This month, Balmain creative director Olivier Rousteing joins CNN Style as guest editor. He's commissioning a series of features on the theme of #diversity -- going beyond fashion to explore issues around politics, gender, family, race and culture.
(CNN)Instagram's fifth birthday party had a guest list stretching to 400 million. That's how many monthly active users the photo-sharing app now has and almost half of them are under 25. In the triumvirate of social media (along with Facebook and Twitter), it's definitely the cool one.