Syrians arriving on the Greek island of Lesbos are part of the largest flow of refugees since World War II. The challenge for the U.N. is to find the funds and political will to address refugee needs while tackling the newly ratified Sustainable Development Goals. Angelos Tzortzinis/AFP/Getty Images hide caption

itoggle caption Angelos Tzortzinis/AFP/Getty Images

Hassan Rouhani, Iran's president, speaks with NPR's Steve Inskeep in New York on Saturday. Rouhani offered his thoughts on Syria's future, the recent nuclear deal between world powers and Iran, freedom of expression and other issues. Bryan Thomas for NPR hide caption

itoggle caption Bryan Thomas for NPR

Iranian President Hassan Rouhani prepares to speak with NPR's Steve Inskeep on Saturday in New York. Rouhani reaffirmed Iran's commitment to the nuclear deal and said his country would be willing to discuss Syria's future with the United States — after ISIS is defeated. Bryan Thomas for NPR hide caption

itoggle caption Bryan Thomas for NPR

Pakistani border guards stopped Afghan refugees from entering in late 2000. Authorities closed the border to stop the influx of refugees into Pakistan, which was already hosting millions of displaced Afghans. HAIDER SHAH/AP hide caption

itoggle caption HAIDER SHAH/AP

A Syrian refugee woman walks to the ferry Eleftherios Venizelos, which functions as a registration center and accommodation for migrants and refugees on the Greek island of Kos, on Aug. 17. The Islamic State has released multiple videos calling on refugees to return to Syria. Alexander Zemlianichenko/AP hide caption

itoggle caption Alexander Zemlianichenko/AP

Syrian refugee woman cries by one of her children as she and family members arrive in an overcrowded dinghy on the Greek island of Lesbos after crossing a part of the Aegean Sea from the Turkish coast, on Saturday. Yannis Behrakis/Reuters/Landov hide caption

itoggle caption Yannis Behrakis/Reuters/Landov

Hungarian border police talk next to a fence, next to a woman who is among hundreds of refugees and migrants caught behind a fence at the Hungarian border with Serbia Wednesday. Armend Nimani/AFP/Getty Images hide caption

itoggle caption Armend Nimani/AFP/Getty Images

Syrian refugees continue to arrive in Jordan, where they are greeted by authorities and sent to refugee camps and temporary settlements. Khalil Mazraawi/AFP/Getty Images hide caption

itoggle caption Khalil Mazraawi/AFP/Getty Images

A migrant girl holds a sign expressing her love to Germany as she arrives at the train station in Saalfeld, central Germany, on Saturday. Hundreds of refugees arrived in a train from Munich to be transported by bus to an accomodation center. Jens Meyer/AP hide caption

itoggle caption Jens Meyer/AP

Images of dead bodies in Syrian prisons, taken by a Syrian forensic photographer, were displayed at the United Nations earlier this year. They were also put on exhibit at the U.S. Capitol in July. Lucas Jackson/Reuters/Landov hide caption

itoggle caption Lucas Jackson/Reuters/Landov