PHOTOS: Panda Twin Cubs at Zoo Atlanta Grow Up

Meet Mei Lun and Mei Huan! The twin giant panda cubs at Zoo Atlanta turn100 days old today -- a milestone date when they are named in keeping with Chinese tradition for good luck. The cubs, born July 15 to 15-year-old mom Lun Lun, are the first giant pandas to be born in the United States in 2013 and the only giant panda twins ever to survive in the U.S.
Zoo Atlanta teamed up with "Good Morning America" to put the pandas' names to a public vote. Five sets of names, all from ancient Chinese idioms, were provided by the Chengdu Research Base of Giant Panda Breeding in China's Sichuan province, and thousands of votes poured in GoodMorningAmerica.com. These winning names, Mei Lun and Mei Huan (pronounced May Loon and May Hwaan), come from the ancient Chinese idiom "Mei Lun Mei Huan," which was used to describe constructed buildings that are tall and magnificent. Until now, the pandas had been known at Zoo Atlanta as "Cub A" and "Cub B."

Click through to see the cubs' adorable development from birth to today.