During pregnancy, due to the bidirectional traffic through the placenta, chimera cells or DNA gets into the mother's and her fetus' body. This is the phenomenon of fetal and maternal microchimerism. These cells, even decades after the birth, can be detected in the host. Despite the fact that a lot of research-team deals with this phenomenon, the importance of microchimerism in health and diseases remains little known. In this article, we aimed to give an overview of the current state of science about this topic. The possible role of microchimerism studied mostly in the pathogenesis of autoimmune processes, non-autoimmune diseases and tumors, or even in the regression of them; it can be as well as a possible component of transplant immunology. The phenomenon of microchimerism could mean important opportunity in the non-invasive prenatal diagnosis, cutting off the currently associated risk of abortion. Due to the constantly developing cell identification- and enrichment procedures, it is expected to be revealed in more and more processes of the human body, that microchimera cells and DNA, as an inheritance of pregnancy, play a role in them.