Giant panda cub Bao Bao is given a cake to enjoy on her second birthday, at Smithsonian's National Zoological Park, in Washington, DC, August 23, 2015. Bao Bao's second birthday comes a day after her mother, 17-year-old Mei Xiang, gave birth to twins, 22 August. This is only the third time a giant panda living in the United States has given birth to twins. (Photo by Michael Reynolds/EPA)
