In pictures: Ai Weiwei's Sunflower Seeds at Tate Modern

Ai Weiwei poses with a handful of seeds at this morning's press view Photograph: Lennart Preiss/AP Workers rake the 'seeds' in preparation for the opening; more than 100 million are said to be spread across the floor of the hall Photograph: Peter Macdiarmid/Getty Images A close-up photograph of some of the seeds, each kiln-fired twice: once before being hand-painted, once again after. Each is unique Photograph: David Levene for the Guardian Tate Modern staff begin to lay out the seeds Photograph: Peter Macdiarmid/Getty Images Visitors will be encouraged to walk across the installation and pick the seeds up – but not to steal them Photograph: Stefan Wermuth/Reuters They will even be allowed to lie down, should they choose ... Photograph: Fiona Hanson/PA A close-up of the seeds piled on the floor of the Turbine Hall Photograph: David Levene for the Guardian Photograph: David Levene A photographer zooms in for a worm's-eye view Photograph: Stefan Wermuth/Reuters Sunflower seeds are an omnipresent Chinese snack, but also were a common food during the harsh years of the Cultural Revolution. Some may also think of sweatshop-powered globalisation Photograph: David Levene for the Guardian Photograph: David Levene/For the Guardian The show runs until May 2011 Photograph: David Levene for the Guardian Photograph: David Levene/For the Guardian