Vivian Maier worked as a nanny but kept up an amazing life as a prolific photographer of life on the streets of Chicago. The enormous trove of her negatives has recently led to major exhibitions around the world. A historian named John Maloof set off this furor when he purchased a box of thirty thousand prints and negatives being auctioned away by a storage facility. Little did he know that he had stumbled upon an incredible record of mid-century life in the big city.