In 2011, he launched The Precious Heritage Project with the goal of increasing recognition of Vietnam's diverse tribes through stories examples of their craftsmanship, and large scale portraits of each group in their traditional clothing.

[3] On January 1, 2017, Réhahn opened the Precious Heritage Art Gallery Museum with the goal of creating a single place to preserve the artifacts and costumes he'd been given by the chiefs of many tribes as well as to share the portraits, stories and musical traditions of the ethnic groups.

Réhahn completed his primary mission of meeting all 54 officially recognized ethnic groups in September 2019 and continues his research to discover the numerous subgroups that are spread throughout the country.

[6] It was there that he captured "Hidden Smile",  the photograph of Madame Xong, captain of a small tourist riverboat, which has since been published in more than 100 articles worldwide.

Created to foster intellectual curiosity and open the doors to understanding and communication with the diverse ethnicities present in Vietnam, the museum attracts both tourists and locals.

[13] Displayed alongside the photographs are more than 65 authentic tribal costumes, some of them were given by the village chief as a means of preservation since many of these garments are no longer being made.

Inspired by the Impressionist and Post-Impressionist movements' focus on light, fleeting moments, and the emotional essence of a scene, the artist pioneered this technique.

The resulting photographs evoke a sense of movement, light play, and the fleeting beauty of nature, reminiscent of the works of Monet, Degas, Cézanne, and Van Gogh.

Her portrait was featured on the cover of the photographer's first book – Vietnam, Mosaic of Contrasts, Volume I and garnered international press attention.