It has been 100 days since two baby pandas, known for three months as Cub A and Cub B, were born at Atlanta's zoo.

Today, they were officially named.

At a naming ceremony Monday morning, Zoo Atlanta announced Cub A will be called Ya Lun and Cub B will be called Xi Lun. According to a zoo press release, Ya means "elegant" and Xi means "happy". The cubs' mother is named Lun Lun.

"The 100 Day Celebration ... is an ancient Chinese tradition that holds that when a child reaches the 100th day of life, he or she has survived the fragility of infancy and may be considered on track for a successful future," the release explained.

Both pandas are females. The zoo said five older siblings of the pair were born in Atlanta and now live at Chengdu Research Base of Giant Panda Breeding in China. (If you were wondering, pandas returning to China travel by plane, with human assistants.)

Since they were born in September, Ya Lun and Xi Lun have spent much of their time in the spotlight, despite not being able to walk or go outside (or even open their eyes at the beginning). The zoo has released updates on their progress every few days via Twitter and YouTube.

Thousands of people have watched videos like this one, showing a routine veterinary exam of a 52-day-old cub (it's unclear whether this is Ya or Xi).

In a nod to the pandas' popularity, when it came time to consider names, the zoo asked the public to choose among seven potential names provided by a panda conservation partner in China. More than 27,000 people voted between Nov. 21 and Dec. 4.

According to Zoo Atlanta, it is one of four U.S. zoos housing giant pandas, all of which are on loan from China. The collaboration between the Chinese government and American zoos is meant to help boost the long-endangered panda population.

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