During more cordial times, Donald Trump (left) talks with New Hampshire Union Leader Publisher Joe McQuaid during a Politics and Eggs breakfast in Manchester, N.H., in 2014. Jim Cole/AP hide caption

Indigenous people attend the trial of two army officers accused of keeping Mayan Indian women as sex slaves during Guatemala's 36-year civil war. Johan Ordonez/AFP/Getty Images hide caption

Prosecutor Robert Zauzmer (left) from the U.S. attorney's office in Philadelphia will head up the Justice Department's effort on pardons. Brad Bower/AP hide caption

When so-called senescent cells were removed from mice, they were healthier and lived longer than mice that still had the cells. Philippe Merle/AFP/Getty Images hide caption

British Prime Minister David Cameron wants to cut migration, and part of the government's plan calls for some foreign workers to leave if they are making less than 35,000 pounds (about $50,000) annually. Ben Pruchnie/Pool/AFP/Getty Images hide caption

A patient suffering from Guillain-Barre syndrome recovers in a hospital ward in San Salvador on Jan. 27. Researchers are trying to determine whether there is a link between the disorder, which can cause weakness and paralysis, and the mosquito-borne Zika virus. Marvin Recinos /AFP/Getty Images hide caption

Scientists have the ability to use DNA from three adults to make one embryo. But should they? A. Dudzinski/Science Source hide caption

A customer looks at a book at Amazon Books, the first brick-and-mortar retail store for the online retail giant, on Nov. 3 in Seattle. Elaine Thompson/AP hide caption

Guillermo & Joaquin, 2013. Catherine Opie/Courtesy of Regen Projects, Los Angeles hide caption