From PBS - Johnson considers how the invention of the mirror gave rise to the Renaissance, how glass lenses allow us to reveal worlds within worlds and how, deep beneath the ocean, glass is essential to communication. He learns about the daring exploits of glassmakers who were forced to work under threat of the death penalty, a physics teacher who liked to fire molten glass from a crossbow and a scientist whose tinkering with a glass lens allowed 600 million people to see a man set foot on the moon. The link between the worlds of art, science, astronomy, disease prevention and global communication starts with the little-known maverick innovators of glass.