Ao dai through history are on display at the Ao dai Museum on Long Thuan street, district 9, Ho Chi Minh City. (Photo: VNP/VNA)

Ao dai is the main costume of performers in ca tru (ceremonial singing), which was recognised by UNESCO as an intangible cultural heritage in need of urgent safeguarding in 2009. (Photo: VNP/VNA)

Xoan singers of Phu Tho province wear ao dai. Xoan singing from the northern province of Phu Tho was added to the United Nations Educational, Scientific and Cultural Organisation’s (UNESCO) list of intangible cultural heritage of humanity in 2017. (Photo: VNP/VNA)

Vietnamese traditional long dress (Ao dai) festival in Hanoi. (Photo: VNP/VNA)

Ao dai has become the daily uniform of female students in Hue. (Photo: VNP/VNA)

Ao dai is a traditional costume in weddings and engagement and many other major ceremonies in Hanoi. (Photo: VNP/VNA)

Italian Ambassador to Vietnam Cecilia Piccioni wears her red ao dai by designer Chula at a festival in the Temple of Literature in Hanoi. (Photo: VNP/VNA)

Ao dai collections by well-known designers are shown at the Ao dai Festival at the Temple of Literature in Hanoi. (Photo: VNP/VNA)