Over the past century and a half, visitors have traveled through Yosemite on foot, by carriage, by tram and by car. Now some regions will be once again be accessible only by foot, to protect delicate regions of the park. Courtesy Yosemite National Park Research Library/KQED hide caption

itoggle caption Courtesy Yosemite National Park Research Library/KQED

Portugal's Cristiano Ronaldo takes a water break during the 2014 World Cup soccer match between Portugal and the U.S. in Manaus, Brazil, on June 22. Siphiwe Sibeko/Reuters/Landov hide caption

itoggle caption Siphiwe Sibeko/Reuters/Landov

The CRISPR enzyme (green and red) binds to a stretch of double-stranded DNA (purple and red), preparing to snip out the faulty part. Illustration courtesy of Jennifer Doudna/UC Berkeley hide caption

itoggle caption Illustration courtesy of Jennifer Doudna/UC Berkeley

A rendering of Neanderthals cooking and eating. The ancient humans inhabited Europe and western Asia between 230,000 and 29,000 years ago. Mauricio Anton/Science Source hide caption

itoggle caption Mauricio Anton/Science Source

Dorothea Handron suffered an infection after a surgeon unknowingly pierced her bowel during a hernia operation. She became so ill that doctors placed her in a medically induced coma for six weeks. Jim R. Bounds/AP Images for Kaiser Health News hide caption

itoggle caption Jim R. Bounds/AP Images for Kaiser Health News

Twenty-nine percent of all cellphone owners described their phone as "something they can't imagine living without," according to a Pew Research Center survey. iStockphoto hide caption

itoggle caption iStockphoto