The six-month show opened on Thursday on a stage in Japan's industrial heartland of Aichi, 250km west of Tokyo.
 
The theme of the current Expo, which traces its roots to the 1851 Great Exhibition in London, is Nature's Wisdom, with 121 countries hosting displays meant to show the link between technology and the environment.

"I hope this exposition will become the starting point for us to think about coexistence of humans and nature," Japanese Prime Minister Junichiro Koizumi told more than 2000 invited guests at the forest park, which will open to the general public on Friday.

"I hope this exposition will become the starting point for us to
think about coexistence of humans and nature"

Japanese Prime Minister Junichiro Koizumi

"The key to make environmental protection compatible with
economic development is technology.

By managing to promote both environmental protection and economic prosperity, we must pass on this beautiful Earth to our children," Koizumi added.

The event is expected to draw about 15 million people with exhibits on everything from advanced robots to a frozen mammoth dug up in Siberia.