Like Vivian Maier's selfie, in which half of her face is visible under the glare of the sun while the other is hidden, she is known by most people as a nanny.

In fact, her hidden side was a photographer.

At a time when women photographers were rare and no smartphones to take selfies, she was a pioneer.

Maier took photos not for money or fame, but simply to record history.

Born in New York in 1926, she took more than 100,000 photos during her lifetime.

Yet this talent was only discovered two years before her death in 2009.

An exhibition showcasing her works and life story debuted at Today Art Museum in Beijing in March and will run until June 30.