Ai Weiwei's Sunflower Seeds is an artwork of staggering scale and meticulous craftsmanship. One hundred million individually handmade porcelain sunflower seeds carpeted 1,000 square metres of the Tate Modern's Turbine Hall to a depth of 10 centimetres, weighing a total of 150 tonnes. Each tiny seed underwent a 30-step process, hand-painted and fired at 1,300 degrees Celsius by over 1,600 artisans in Jingdezhen over two and a half years.