The Bureau International des Expositions also recognises the Milan Triennial Exhibition of Decorative Arts and Modern Architecture, on grounds of historical precedence, provided that it retains its original features.

[3] Countries, international organizations, civil societies, and corporations are allowed to participate in World Expos.

The themes of World Expos address a universal challenge facing humanity, and international participants may design and build their own pavilions.

Pavilions participating at a World Expo can also be large, sometimes 5,000 to 10,000 square metres in size, mini city blocks in themselves and sometimes more than several stories in height.

The largest pavilion may be no larger than 1,000 square meters, and the Expo site must not exceed an area of twenty-five hectares.

There are blurred lines between Specialized and World Expositions prior to the 1996 amendment of the BIE's constitution.

184 countries are member states of the BIE:[4] Australia was a signatory to the treaty[12] and won the right to hold the 1988 World Exposition.

[16] The United States' membership in the BIE was revoked in June 2001[17] due to non-allocation of funds by the U.S. Congress for two years.

However, the withdrawal "had strong, adverse consequences for states and localities that wish to host an exposition on U.S. soil.

The anthem of the Bureau International des Expositions (BIE) is the starting part of the 4th Movement of Dvořák's Symphony No.