[Avenger2099]

Just thought I'd point this out to everyone. There's an anime called Simoun which is about a world where most people choose their gender at seventeen. Everyone is born female and then goes to this place called 'The Spring' where they choose their gender.

Of course... in the actual anime even the men look rather feminine and they all have female voices which is kind of odd. Still, great anime, I would recommend it and it has process (though it's very, very slow.)