Nanovesicles or nanostructures that resemble tiny bacteria of less than 0.5 m m in diameter were finded as contaminants in commercial fetal bovine serum, and were responsible for the cytotoxicity on cell monolayer cultured in vitro. Then, the agent was isolated and classified as Nanobacterium sanguineum, it was associated with kidney stone formation and more recently with other pathologies producing calcification. In the other hand, none researchers do not accepted the existence of these bacteria. More studies must be done to determine whether the nanostructures observed are bacteria