This is the story of how a change in how iron was made in the 18th century changed the world forever, and of the men and women who made it happen. The production of iron around 700BC was so important that it was called the Iron Age. This was the second Iron Age. Iron made the machines of the industrial revolution; it transformed transport with iron ships and iron trains running on iron rails; iron- framed buildings were the prototypes of the modern skyscraper. But progress was bought at a price: the knife grinders of Sheffield were lucky to survive to reach their 30th birthday before dying of ruined lungs. The women chain makers of the Black Country were described in the 19th century as "The White Slaves of England." This is a story that mixes brilliant innovation with hardship and struggle.