Chinese artist Ai Weiwei has installed a landscape of sunflower seeds on the floor of the Tate Modern Turbine Hall.

There are over 100 million of them.

And each one is handmade in porcelain.

The exhibition opened yesterday, and is the latest commission in The Unilever Series, (which has previously seen work commissioned from Louise Bourgeois, Anish Kapoor and Olafur Eliasson) covering the east end of the Turbine Hall.

Visitors are invited to walk across the surface of the work and discover that each seed is in fact a unique porcelain replica, one of over 100 million individually handmade objects which have been specially produced for the commission.

This is the largest work Ai has made using porcelain, one of China’s most prized exports, with which he has previously created imitation fruit, clothes and vases. Although they look identical from a distance, every seed is different, and far from being industrially produced, ‘readymade’ or found objects, they have each been intricately handcrafted by skilled artisans.

All of them have been produced in the city of Jingdezhen, which is famed for its production of Imperial porcelain. Each ceramic seed was moulded, fired at 1300°C, hand-painted and then fired again at 800°C. Over the course of two years, over 100 million of these were made, forming a mass of objects that weighs over 150 metric tonnes, covering 1000 square metres. The casual act of walking across their surface contrasts powerfully with the precious nature of the material and the effort of its production.

For Ai, sunflower seeds - a common Chinese street snack shared by friends - carry personal associations from the 1966-76 Cultural Revolution. While individuals were stripped of personal freedom, propaganda images depicted Chairman Mao as the sun and the mass of people as sunflowers turning towards him.

Yet Ai remembers the sharing of sunflower seeds as a gesture of human compassion, providing a space for pleasure, friendship and kindness during a time of extreme poverty, repression and uncertainty. There are also contemporary resonances in the work, with its combination of mass production and traditional craftsmanship inviting us to look more closely at the ‘Made in China’ phenomenon and the geopolitics of cultural and economic exchange.

Sunflower Seeds is a sensory and immersive installation, which visitors can touch, walk on and listen to as the seeds shift beneath their feet. However, the tactile, engaging nature of this work also encourages us to consider highly pertinent questions about ourselves and our world.

What does it mean to be an individual in today’s society? Are we insignificant or powerless unless we act together? What do our increasing desires, materialism and number mean for the future?

Ai Weiwei has said “From a very young age I started to sense that an individual has to set an example in society. Your own acts and behaviour tell the world who you are and at the same time what kind of society you think it should be.”

The installation will remain at the Tate until the 2nd of May 2011 and admission is free.