This week, a new documentary about photographer Vivian Maier opened in Chicago. She's the Chicago nanny who was also a secret photographer, and who many now believe is one of the great street photographers of the 20th century.

When Jay Shefsky first introduced us to Vivian Maier in December 2010, she was only known to a small group of street photography devotees. But his video immediately went viral. Within a few weeks, it had been viewed more than 300,000 times on our own website and on YouTube.

Since then, Vivian Maier's popularity and importance has skyrocketed. Jay Shefsky has since done two follow-up reports. This week, we will revisit all three stories. Take another look at that original story that introduced us - and many others - to this remarkable artist.