Their efforts eventually paid off. In the early 2000s, after advances in artificial insemination, Chinese breeding centers became filled with piles of baby pandas. And in 2005, Mei Xiang, the second female to be loaned to the National Zoo, gave birth to a healthy male cub named Tai Shan. Smith remembers meeting Tai Shan when she joined the zoo a few years later as the Curator of Mammals. “It was like meeting a rockstar,” she says. “I was a little nervous. Will he like me?”

But Tai Shan’s successful birth heralded a seven-year reproductive drought. By 2012, Mei Xiang’s odds of having another cub were less than 5 percent. “Given her age, and how long it had been since she’d had Tai Shan, everyone thought that was it,” says Smith. “Every one of us on the panda team said: she’s not going to do this. But when you work here, you do at least one impossible thing every day. We thought that if we could get the conditions right, her environment would tell her that it would be a good time to have a cub.”

Pandas give birth within cosy dens, so the team fenced off a little nook in the corner of her enclosure, about the size of an eight-person dining table. They also reduced the number of people who had access to that enclosure, and the hours they spent with her. And after all that effort, on September 2012, Mei Xiang finally gave birth to another four-ounce cub—which died six days later. Its lungs weren’t fully formed. There was nothing the team could do.

The experience was tragic, but Smith suspects that it “got Mei Xiang’s engine running again,” because a year later, it looked like she was pregnant again. The problem is that pandas go through regular pseudopregnancies, during which they’ll behave as if they are carrying a fetus even when they’re not. Experts can’t tell the sham pregnancies from the real ones, so everyone’s on tenterhooks until a pup actually emerges.

That happened on August 23, 2013. Just after midnight, Smith got a call saying that Mei Xiang was displaying all the behaviors that signal an imminent birth: restlessness, cradling objects, and genital licking. (“My husband would joke that the phone would ring at the middle of the night because the panda was licking herself,” she says.) She raced down to the zoo, and her team of a half-dozen keepers kept a long vigil, watching the maybe-mother for hours on a wall of webcams.

At 5:32 p.m., in the middle of the Friday rush hour, Mei Xiang’s water broke. She dropped the Kong toy she was cuddling, and then, from the other end, dropped a baby panda into the world.

Baby Bao Bao.

(Smithsonian's National Zoo)

It’s a weird thing to raise a panda in America, because all the pandas there—even those born on U.S. soil—are considered loans from China. And Chinese experts, who tend to be more hands-on than their American peers, wanted the zoo team to do a check-up on the baby as soon as possible. That meant extracting it from the arms of its 200-pound mother, who—and do not forget this—is a bear. “Some female pandas are mellow about you being in their space, but Mei Xiang has never been that panda,” says Smith.