Pablo Ross of the University of California, Davis, inserts human stem cells into a pig embryo as part of experiments to create chimeric embryos. Rob Stein/NPR hide caption

Even when results from studies involving children are available, they frequently aren't published in medical journals. Cultura RM Exclusive/Getty Images hide caption

Massachusetts Gov. Charlie Baker signs a pay equity act into law at the Massachusetts State House on Monday in Boston. Elise Amendola/AP hide caption

Orange sediment laced with heavy metals is visible in the path of water coming out of the Natalie/Occidental Mine in southwestern Colorado. This mine is one of dozens on a proposed Superfund listing pending with the EPA. Several mines in the area have been leaching the tainted water for years — well before the Gold King Mine spill. Grace Hood/Colorado Public Radio hide caption

Cover of the first trade collection of the 1980s comics series Suicide Squad. DC Comics hide caption

U.S. marathon swimmer Haley Anderson won a silver at the 2012 Olympics when she lost a sprint to the finish by four-tenths of a second. Anderson, 24, will be swimming the 6.2-mile race again in Rio, where much of the pre-race attention has focused on the polluted waters. Melissa Block/NPR hide caption

Zelda Fichandler co-founded Arena Stage in Washington, D.C., with her husband, Tom Fichandler, and drama teacher Edward Mangum. She is seen here with her husband in 1971. Courtesy of Arena Stage hide caption