After covering corpses in Stiff and ghosts in Spook, Mary Roach tackled a new (for her) subject in Bonk, sex. In this video from Slate Magazine, Mary Roach discusses the book, including how she and her husband were the first people to be filmed in 4D ultrasound while having sex. Seems up til now, no one knew exactly where the parts inside interacted. Ultrasound pic included.