Red chairs fill a main street in Sarajevo on Friday as the city marks the 20th anniversary of the start of the Bosnian war. Officials lined up 11,541 chairs in 825 rows to represent the 11,541 Sarajevans who were killed during the siege. Amel Emric/AP hide caption

Bill Gates addresses an energy innovation summit in Maryland in February. The Microsoft chairman told NPR in an interview for Weekend Edition that teachers should be evaluated, but that the reviews should not be made public. Paul J. Richards/AFP/Getty Images hide caption

An artist's impression of a group of Yutyrannus. The 30-foot-long dinosaurs were covered with downy feathers — likely to keep the animals warm. Dr. Brian Choo/Nature hide caption

Guerrilla grafter Tara Hui grafts a fruiting pear branch onto an ornamental fruit tree in the San Francisco Bay Area. She doesn't want the location known because the grafting is illegal. Lonny Shavelson for NPR hide caption

Rascal Flatts is one of the most popular country groups of the last decade. Courtesy of the artist hide caption

Gideon Shoes co-founder Matt Noffs with youth from The Street University, the nonprofit youth center that launched the fair trade company. John Burnett/NPR hide caption

Unalaska's Sgt. Jennifer Schockley has earned fans worldwide for her local police blotter. Alexandra Gutierrez/KUCB hide caption

Photographer Mick Rock in New York City, 2011 Michael Loccisano/Getty Images hide caption