Gene Gangarosa’s 70-year career spans a revolution in the prevention, treatment, and control of enteric (intestinal) diseases. His groundbreaking intestinal biopsy studies of cholera patients showed the gut wall was intact, refuting previous beliefs, including harmful “starvation therapy.” This finding encouraged other scientists to develop oral rehydration therapy (ORT)—a simple and inexpensive way to replace fluids and electrolytes lost through vomiting and diarrhea, which could be given readily at home. This innovation dramatically improved health outcomes for intestinal illnesses. ORT saves the lives of one million children annually; in 1978, Lancet heralded it as “potentially the most important medical advance of this century.” Dr. Gangarosa also described chronic pathological changes now called environmental enteropathy, a deadly, stunting, debilitating malabsorption syndrome caused by frequent intestinal infections. He has been involved with safe water initiatives to prevent diarrheal diseases at the household level, including research on point-of-use disinfection; dedicated teaching, mentorship, and leadership; encouragement of ongoing advances and epidemiological evaluation; and philanthropic support. But Now They Are Angels gives one of the widest accounts of scientific discovery that any person has ever witnessed, from the standpoint of an elder statesmen involved in nearly every aspect of this lifesaving branch of public health.