From the ultra clean environment of a microchip factory to the railway engineer who lifted a city to install sewers, innovation expert Steven Johnson traces the surprising journey from dirty to clean in our lives. He discovers the unsung heroes of this transformation, like the doctor who secretly experimented with a deadly chemical to treat the water supply, and the storekeeper who revolutionised cleanliness in the home.

A five-part series presented by best-selling author Steven Johnson (Where Good Ideas Come From, Everything Bad Is Good for You), investigating the little-known stories of revolutionary innovations.