It is a fibre and a fabric that is part of many people's daily lives, it grows wild on at least three continents, it has been woven into cloth and traded all over the world for thousands of years. And when machines made possible the mass production of cotton, its story became entwined with the history of human slavery: making fortunes for a few, and condemning many to a life of misery. So what are the milestones in the history of cotton? And why has it always proved such a popular clothing material across the centuries and across the world? Bridget Kendall is joined by four textile historians to trace cotton's origins and its evolution into one of the world's most important global commodities: Sven Beckert, Professor of History at Harvard, Prasannan Parthasarathi, Professor of History at Boston College, Giorgio Riello, Professor of Global History and Culture at the University of Warwick and the President of the Textile Society Mary Schoeser. Photo: Cotton yarn (Getty Images)