Girls carrying school bags provided by UNICEF walk past destroyed buildings on their way home from school on March 7 in the rebel-held al-Shaar neighborhood of Aleppo, Syria. So many people have fled the city and so much of its infrastructure has been destroyed that nighttime satellite images show 97 percent less light there compared with four years ago. Zein al-Rifai/AFP/Getty Images hide caption

itoggle caption Zein al-Rifai/AFP/Getty Images

A Mercy Corps warehouse is filled with hygiene kits for distribution in Syria. Deborah Amos/NPR hide caption

itoggle caption Deborah Amos/NPR