" By the century’s end, all doctors had to have a college degree, a four-year medical degree, and an additional three to seven years of residency training in an individual field of practice—pediatrics, surgery, neurology, or the like. In recent years, though, even this level of preparation has not been enough for the new complexity of medicine. After their residencies, most young doctors today are going on to do fellowships, adding one to three further years of training in, say, laparoscopic surgery, or pediatric metabolic disorders, or breast radiology, or critical care. "

― Atul Gawande , The Checklist Manifesto: How to Get Things Right