Functional magnetic resonance imaging--or fMRI--has made quite a splash since its introduction a decade ago. Operating at spatial dimensions and time-scales far finer than previous brain-scanning techniques, it has sparked great excitement by letting us finally watch the brain at work. Thousands of fMRI studies have explored a wide range of differences in brain activation: adolescents versus adults, schizophrenic and normal minds, the empathetic and the impassive. Researchers have used fMRI to draw bold conclusions about face and word recognition, working memory and false memories, people anticipating pain, mothers recognizing their children, citizens pondering ethical dilemmas--not to mention why many consumers buy Coke even though they really prefer the taste of Pepsi. Psychologists have praised fMRI for finally making their science more quantifiable. And cognitive neuroscientists have cited the scans heavily in the recent, vast expansion in understanding of the brain.