Mexican artist Frida Kahlo revealed her vulnerable side to only very few people. Only her lover, photographer Nickolas Muray, captured moments as intimate as these. Her life was severely impacted by polio and the traffic accident she suffered at a young age, which did not hinder her art. The black-and-white photos of her stand in sharp contrast to the artist's brightly colored oeuvre.

Frida Kahlo meticulously maintained a collection of photographs by some of the top photographers of her time, including Tina Modotti and Man Ray. Snapshots like this one of her husband, painter Diego Rivera, were also among her collection. Kahlo liked to "sign" her works with a lipstick kiss or note her thoughts in the margins.

Kahlo was born in 1907 on the outskirts of Mexico City. Back then, family photo albums, carefully bound in leather, could be found in every well-to-do household. Her father, Guillermo Kahlo, was a photographer and passed on his love for the art. Frida often posed for him and her private photo collection later became an essential part of her own artistic identity.

Guillermo Kahlo was German and Frida later claimed he also had Hungarian-Jewish roots. He immigrated to Mexico in 1891 and became one of the most renowned photographers in the country. Her mother, Mathilde Calderón, had indigenous Mexican and Spanish roots and was "terribly exaggerated in religious things," according to Frida.

Guillermo Kahlo created countless artistic portraits of his daughter. She often accompanied him on excursions and helped him develop his photographs. Frida's right leg was left partially handicapped after she contracted polio at the age of six.

She was already acquainted with handicap, but in 1925 Kahlo's life would change dramatically once again. She was severely wounded in a bus accident and nearly died of internal bleeding. Restricted to her sick bed, she began to keep a journal and paint. Hospital visits would become a regular part of her life. She built a special apparatus which allowed her to paint while lying down.

At the age of 22, Kahlo married 43-year-old Diego Rivera, Mexico's most successful artist at the time. She admired him and assisted him with his massive wall-sized works. Rivera called his wife "his dove" and enjoyed seeing her in brightly colored traditional Mexican dresses like this one.

In 1932, Diego Rivera was commissioned by the car maker Ford to create a large political mural. The artist was fascinated by the abstract language of the industrial world. Kahlo traveled with him to the United States and exhibited her works for the first time in San Francisco, where she was celebrated. Pictured are two of Kahlo's photos from Detroit. Two years later, the couple returned to Mexico.

Rivera had numerous extramarital affairs and Kahlo was often unhappy in her marriage. The pair divorced, but remarried again in 1940. Kahlo was also involved in other relationships, with both men and women. Her lover, photographer Nickolas Muray (left), documented her life up until her death in 1954 at the young age of 47.

Frida Kahlo's private collection includes 6,500 photographs. It wasn't made available to the public until 2007, many years after her death. Curator Pablo Ortiz Monasterio selected 241 photos, which are on show at the MARTA Herford museum in northern-central Germany through May 10, 2015.