Ao dai has experienced many modifications since its original version. Ao tu than, which had been worn by Vietnamese women centuries before the Ao dai evolved into the five-paneled dress which is known as the closest form to the Ao dai. The older version of Ao dai then has five flaps: two in the back, two in the front and one under the front lap. Ao dai, however, is more tight fitted and has higher collar without a bodice underneath.