This chapter poses a series of questions designed to emphasize some of the more intriguing current concepts in clinical and basic placentology that remain poorly understood, yet are very relevant to researchers and clinicians whose day-to-day activities focus on the placenta. Normal pregnancy is characterized by warm skin, prominent veins, and a tendency to dizziness, termed orthostatic hypotension, when lying flat. Extravillous cytotrophoblast (EVT) cells proliferate, invade, and differentiate as they surround and transform the distal segments of the uteroplacental spiral arteries. Abnormal uterine artery Doppler at 22 weeks' gestation confers a five-fold increased risk of all forms of preeclampsia, but a much greater risk of early-onset disease with associated intrauterine growth restriction (IUGR). The utility of uterine artery Doppler is improved when targeted to women with risk factors for placental dysfunction, especially women with abnormal first or second trimester screening results.