The human placenta is the primary life-support organ for the developing fetus. It integrates a multi-organ system's functions but comprises only five major cell types. It is a highly metabolic organ, consuming 40% of the total oxygen used by the entire conceptus while accounting for only 20% of its total mass. This high metabolic activity supports the placenta’s extensive transport function, its manufacture of hormones, and the biochemical processing of nutrients. The precise functions of the cells within the placenta that underlie these processes remain poorly defined. This thesis reports that some of the metabolic processes that have been traditionally assumed to be restricted to other placental cell types are primarily driven by a layer of progenitor trophoblast cells, the cytotrophoblast, which have been ignored as significant contributors to placental metabolic function.