A poster put out by the U.S. Children's Bureau in 1918. Francis Luis Mora/Library of Congress hide caption

Samantha Pierce of Cleveland has a 7-year-old daughter, Camryn. In 2009, Pierce gave premature birth to twins. The babies did not survive. Scientists say black women lead more stressful lives, which makes them more likely to give birth prematurely and puts their babies at risk of dying. Dustin Franz for NPR hide caption

Nedal Said risked everything to rejoin the scientific community. Erik Nelson Rodriguez for NPR hide caption

Carmen Bachmann founded "Chance for Science," a website that connects refugee academics with scientists working in Germany. Thomas Victor for NPR hide caption

Jim Allison in his lab at the University of Texas MD Anderson Cancer Center in Houston. Scott Dalton for NPR hide caption

Lea Hatouni is a Christian living in the predominantly Muslim Middle East. Like so many other Lebanese, she expects to have to leave Lebanon to start her career after college. Jason Beaubien/NPR hide caption

She's a teenager with a cellphone, surfing the Internet. And she's a Syrian refugee who works in the fields up to 14 hours a day. That's the new life of 15-year-old Fatmeh, seen here in the living room area of her family's makeshift shelter. Dalia Khamissy for NPR hide caption

Ignaz Semmelweis washing his hands in chlorinated lime water before operating. Bettmann/Corbis hide caption

Emergency room doctor Joshua Mugele (left) stands with Dr. Samuel Brisbane at Liberia's JFK Hospital, which saw its first Ebola patient in June. Courtesy of Joshua Mugele hide caption

A prosthetic eye is a work of art custom-crafted for an individual. Rebecca Davis/NPR hide caption