Abigail Tucker’s article in Smithsonian Magazine is a fascinating look at how offspring affect their mothers’ hearts and brains in deep and enduring ways. New research sheds light on why hearts of recently delivered human mothers have shown a remarkable ability to recover from cardiac events. In tests on mice at Mount Sinai Hospital lab, cardiologist Hina Chaudhry and her research team discovered something astonishing: heart cells with DNA that doesn’t match the mother’s own. The mystery cells belong to unborn mice. During pregnancy the fetal mouse cells cross the placenta into the mother’s body, joyriding through her blood vessels until cardiac damage happens, at which point they sense inflammation and make a beeline for her wounded heart. The lab has found that these cells, harvested from mouse placentas, will travel to the damaged hearts of male mice after being artificially implanted in their tails.