"The timing is the most critical challenge," says Dr. JoGayle Howard, a reproduction scientist.
Pandas are notoriously ineffective breeders, so zookeepers leave nothing to chance. CBS News got unprecedented access as the team tried to pinpoint Mei's perfect moment for mating. They bribed the bear with food so they could examine her, and measured hormone levels in her urine.
It's the first time Mei's ovulating since giving birth to her only cub in 2005. Back then, papa bear was the National Zoo's Tien Tien. In the panda world, his genes are quite common, not a good thing when the species is endangered. The goal is to find new blood to prevent inbreeding.
"The problem with inbreeding is that bad genes may rise to the top," Howard says.
The new man in Mei's life is super stud Gao Gao of the San Diego Zoo.
"He's got great sperm," Howard explains. Gao was captured in the wild, brining new and unique DNA to the worldwide panda-breeding program. That means his DNA, paired with Mei's, will increase the panda gene pool — helping ensure that the bears don't become extinct.
"One breeding is a big deal, and it does change the genetics and the dynamics of the population," Howard says.
But the cross-country romance has been complicated — and not at all romantic. The two pandas won't even meet. The deed is done by artificial insemination, using the precious cargo carried from California in a metal can.
Finally, overnight, it was time. The sperm and egg were brought together, and the romance was consummated.
Did it take? Possibly, but it will take up to five months to find out.