Leonardo da Vinci was convinced that sperm came down from the brain through a channel in the spine, but he could never have imagined the mysteries of sex revealed by modern technology. Gynecologist Willibrord Weijmar Schultz of University Hospital Groningen in the Netherlands persuaded eight couples to have intercourse inside an MRI scanner and observed never-before-seen physiological changes. He discovered that, in the missionary position, the penis is shaped like a boomerang. And contrary to the findings of famed sex researchers Masters and Johnson, the uterus does not double in size during intercourse; in fact, it hardly changes at all. "This is basic science," says Weijmar Schultz. "Based on this knowledge, doctors and sexologists can better understand their patients' problems and find new ways of therapy."