In 2010 a hundred million porcelain sunflower seeds were spread across the Turbine Hall at Tate Modern. From a distance the surface reads as grey and uniform; bent over it, one sees that every seed is different. All were shaped and painted by hand over two and a half years by 1,600 people in Jingdezhen, a city that has made porcelain for a thousand years.

The work's layers connect. The sunflower seed was a common image in Cultural Revolution propaganda: Mao the sun, the people the seeds turning towards him. Ai Weiwei inverts it — the mass may look uniform, but each unit is separate and made by hand. The second layer is production: where the label 'Made in China' suggests anonymous mass manufacture in a global market, these objects are entirely handwork, and that labour has a measurable cost. The third is the viewer's position; when the show opened visitors walked on the seeds, but the field was closed off once porcelain dust proved a respiratory risk, and the work could only be seen from the edge.

In the same years Ai Weiwei was under pressure for his citizens' investigation compiling the names of students killed in the Sichuan earthquake; he was detained for eighty-one days in 2011 and his passport was held until 2015. The relation between the politics of his art and its mode of production — using traditional craft in contemporary conceptual work, adopting social media as a medium — also changed how contemporary art relates to centres outside the West.