Preeclampsia is a disorder that uniquely affects pregnancy and profoundly alters the short- and long-term health of the mother and fetus. The pathophysiologic processes that underlie preeclampsia can be thought of in two stages: stage 1, reduced placental perfusion, and stage 2, the maternal clinical syndrome. Multiple pathophysiologic processes influence stage one, affecting trophoblast invasion and placental function. These processes in some women result in stage two, with subsequent maternal inflammatory, metabolic, and thrombotic responses, converging to alter vascular and endothelial health. An increasingly comprehensive understanding of these factors is emerging, which we will introduce in this chapter and which will be detailed in the chapters that follow. The translation of this understanding into clinical trials and ultimately into effective preventive and therapeutic measures remains the ultimate goal of preeclampsia research.