By Meghan Rosen
Update: On August 26, the National Zoo reported that the smaller of the twin panda cubs born to Mei Xiang had died. Zookeepers, who had been caring for the giant panda cub by hand for two days, had been concerned about its fluctuating weight and noted that the days just after birth are a high-risk period.
Update, August 28: The National Zoo reports that both the surviving cub and the cub that died are males fathered by Tian Tian, a male panda at the National Zoo.