This year's expo has been plagued by delays, with many pointing a finger to rampant corruption as the main cause.
Prior to opening, a flash mob of about 20 students wearing tiger masks held an unauthorised protest outside the venue gates, stating that the expo was an example of corporate problems, with much of the public money put into the project lost to corruption.
"I love to think about the future that will begin in a country that has had an extraordinarily beautiful past," said Italian Prime Minister Matteo Renzi who tried to ease tensions on the opening day of the exposition.
"But to construct this future, the only path to follow is one that embraces the world, without any fear or apprehensions," said Renzi on his opening statement. "It's as if Italy has brought the world together for the next six months to take this opportunity to saveur and appreciate the charms of Italy."
Thousands of visitors poured into during the Expo's opening weekend, and 11 million tickets have already been sold for the six-month, agriculture and gastronomy-themed event held at the Palazzo dell’Arte in the city centre, organisers have said.
Organisers are predicting 20 million visitors before the fair ends 31 October, and a 10-billion-euro boost to economic activity.