Your Mom is a Chimera

And so are you! When you were a fetus, you were sending millions of your cells through the placenta into your mom. And she was sending her cells into you, although to a lesser degree. These cells made themselves right at home, differentiating into heart, blood, and even brain cells. This phenomenon is called feto-maternal microchimerism, and is one of the wildest things in placental mammal pregnancy. What? Microchimerism is generally defined as the presence of a small population of genetically distinct cells in an organism.