High-definition video cameras with 30x magnification keep watch over the Boston Marathon finish line, where two bombs detonated in 2013, killing three people and injuring hundreds. Jesse Costa/WBUR hide caption

itoggle caption Jesse Costa/WBUR

Sequencing the genes of a cancer cell turns up lots of genetic mutations — but some of them are harmless. The goal is to figure out which mutations are the troublemakers. Kevin Curtis/Science Source hide caption

itoggle caption Kevin Curtis/Science Source

European Competition Commissioner Margrethe Vestager announces formal charges against Google, accusing the company of abusing its dominant position as Europe's top search engine. John Thys/AFP/Getty Images hide caption

itoggle caption John Thys/AFP/Getty Images