Gen. John "Black Jack" Pershing visits Arlington National Cemetery in 1925. Pershing led the U.S. forces in World War I, the moment when the American military first displayed its might in a major foreign war. The U.S. military suffered heavy losses, but it also expanded dramatically, modernized and became more professional under Pershing's command. Library of Congress hide caption

Allyson and Eddie, clients at the AAC Needle Exchange and Overdose Prevention Program in Cambridge, Mass., say they carry naloxone and try to never use drugs alone to reduce the risk of overdosing. Robin Lubbock for WBUR hide caption

Unsold cars, used and new, are unloaded from tractor-trailers into a parking lot south of Madrid. It's one of the biggest sales areas for used cars and scrap metal near the Spanish capital. Vendors say they're anticipating difficulty selling diesel cars, now that Madrid and other European capitals have announced plans to ban them. Lauren Frayer for NPR hide caption

Don Rickles was jokingly known as "The Sultan of Insult." The Kobal Collection hide caption

In 2003, Acanthamoeba polyphaga mimivirus, also known as mimivirus, was the first giant virus to be described. It's larger than many bacteria, and was found in a water sample from a hospital cooling tower in England. Didier Raoult/Science Source hide caption