In pregnancy disorders such as pre-eclampsia, intrauterine growth restriction (IUGR) and recurrent miscarriage a poorly functioning placenta is thought to be a major component of the disease process. However, despite their prevalence, we currently have no way to fix dysfunctional placentae or directly treat these disorders. Over the past two decades our understanding of the role that stem cells play in organ development and regeneration has expanded rapidly, and over the past 5 years the therapeutic use of stem cells to both regenerate damaged tissues, and act as potent modulators of diseased microenvironments, has become a reality in many organs including the heart, kidney, liver, skin and eye. Over its short lifespan the placenta undergoes rapid and continuous growth and differentiation, meaning that placental 'organogenesis' only truly ends at delivery, and thus stem cells are likely to play important roles in placental function for the duration of pregnancy. Two populations of stem cells exist in the placenta that contribute to this on-going growth and differentiation: trophoblast stem cells and mesenchymal stem cells. This review will address our current understanding of how each of these stem cell populations contributes to successful placental function, how epithelial and mesenchymal stem cell populations are being translated to the clinic in other fields, and whether these advances can teach us anything about how placental stem cells could be used to fix faulty placentae in the future.