The panda exhibit is by far the most popular at the National Zoo. On Monday it received a $4.5 million donation that will help fund program for the next five years.
Tian-Tian and Mei-Xiang arrived at the zoo in 2000 and ever since, the pair has received worldwide attention.
Philanthropist David Rubenstein of the Carlyle group made the generous donation.
"It costs a lot of money to do research for pandas and panda conservation in the wild," said National Zoo Senior Coordinator Brandie Smith. "A donation like this is absolutely phenomenal."
The funds will go into the up-keep of the pandas' habitat, plus studies with colleagues in China that would look into the reproductive science of the endangered animals.
"One of the great things would be to determine the difference between a true panda pregnancy and a pseudo-pregnancy," Smith said.
Washington's pandas have produced only one cub--Tai Shan--who left for China last year.