Preeclampsia, a pregnancy-specific syndrome of hypertension and proteinuria, is one of the leading causes of perinatal morbidity and mortality. Although the initiating factor is unknown, a clearer picture regarding the network mechanisms of preeclampsia has begun to emerge during the past few years. The pathogenesis of preeclampsia can be described as having two stages. The first stage of preeclampsia involves abnormal placental implantation, followed by transition to the second stage of endothelial dysfunction. The link bridging these two stages is considered to be oxidative stress and disrupting angiogenesis. Discovery of the fundamental molecular mechanisms causing preeclampsia may provide a potential for prophylactic intervention and symptom amelioration. In this article, the clinical syndrome and risk factors of preeclampsia will be introduced, followed by the recent advances in our understanding of the pathophysiology of preeclampsia and, finally, research into aberrant placentation will be discussed.