In tropical countries, traditional fermented foods are usually home-made products obtained through spontaneous fermentation or backslopping. They are now facing an evolution aiming at responding to quality, safety and mass production issues. This requires acquisition of knowledge on raw materials, microbial ecosystems and fermentation processes. Vietnam is a laboratory for such studies as traditional fermented foods play an important role in the diet of Vietnamese and as these foods are very diverse. Among the most popular are nem chua (sausage reminding Thai Nham), dua muoi (cabbage reminding Kimchi), tom chua (shrimps) and the well-known nuoc mam. The challenge for these products to enter the industrial era is to reach a level of quality and safety without losing their character. Beside the research for starters to elaborate these products, the world of fermented products is also a world of innovation and the microbial ecosystem of traditional products can also be used for the adaptation of fermented products from other regions, such as wines (from grape or other fruits), for cross-cultural innovations such as soy-yogurts, for technology transfer from one fermentation (soy sauce) to another one (fish sauce) and for evolution of traditional products towards higher nutritional qualities such as nem chua nam (replacing part of the sausage meat by mushrooms). Finally, these complex microbial ecosystems are a source of probiotic, antimicrobial compounds and biocatalysts, which can benefit health and improve food processes worldwide. After a presentation of Vietnamese traditional fermented foods, this article aims at illustrating the diverse applications of research on fermented products through examples obtained in past research and in the Tropical Bioresources and Biotechnology project.