China today unveiled a multi-billion dollar world expo at its gleaming commercial hub, Shanghai. 191 nations, including India and 50 international organisations are taking part in the expo, the first any developing country has hosted.The six-month-long expo, got off to a rousing start with an extravagant display of fire works fireworks lighting up the Shanghai sky line. Hollywood actor Jackie Chan performed at the event.Chinese President Hu Jintao hosted a lavish dinner to large gathering of world leaders including French President Nicolas Sarkozy, Palestinian President Mahmoud Abbas, Chairman of North Korea's Supreme People's Assembly Kim Yong Nam.President Pratibha Patil is also scheduled to visit the expo during her trip to China next month.Ahead of the expo, China has lifted a 20-year-old ban on entry for foreigners with HIV and AIDS.This is the first time that world expo is being held in a developing country ever since the exhibition was first organised in London in 1851.The Expo will open tomorrow and 70 million people are expected to visit pavilions of different countries designed to reflect the urban sustainability theme of "Better City, Better Life".