In a nutshell: Inventing Abstraction, 1910–1925, running at the Museum of Modern Art (11 West 53 Street, New York, NY) through April 15, 2013. It’s a great exhibition that I recommend highly.
Instead of waiting for my review, which may never come, you can read this review from The New York Times. For now, I just want to tell everyone that this exhibition is awesome and if you are within range, you should go see it.
Also see this review in The New Yorker.