The immune system typically protects our bodies from infection and illness by fending off foreign invaders. During pregnancy, however, the mother’s immune system works in an unusual manner to support the health and development of the baby. One particularly important role for cells of the immune system during pregnancy is to promote the growth of the mother’s blood vessels, which provide the growing baby with nutrients. This image of a mouse uterus captured early in pregnancy shows a large number of immune cells interacting with the mother’s blood vessels to facilitate vessel growth and nurture a healthy pregnancy.