And Tai Shan and Bao Bao have had their own cubs in China. The youngest cub, Xiao Qi Ji ("Little Miracle" in Chinese), was born in August 2020 and is still living in the National Zoo with his parents.

For Winslow, the breeding program is impressive, and all the cubs are her "favorite".

"I think the most exciting time was when after Mei Xiang and Tian Tian came and we were starting with a breeding program. And the whole excitement about would they breed and if they breed? Would she get pregnant? You don't know what's going to happen," said Winslow.

"And then when we had babies that were just on the cubs were just so exciting. They are so helpless. Those little baby pink things are just tiny, and I remember being so impressed that they couldn't do anything except suck and scream and they have the loudest voices for their size louder than anything I've ever seen in my life. They were amazing," she recalled with a big smile.

As a mother of two sons herself, Winslow admired Mei Xiang as "such a good mother. She actually taught me about mothering, about patience."

Winslow said that she "cannot help but be optimistic" for the future of the US-China cooperation program on pandas.

"We have done this for 50 years. Why should it not go on? Why shouldn't scientists be able to cooperate with each other?" she said. "I am very optimistic. I think it's something that will last between the two countries.

"When I was young and starting, I just thought it was exciting to be there and learn and watch and be involved. And 50 years later, I think about how long that has been in my life," Winslow said. "I think about the extraordinary cooperation collaboration that has gone on for so long between China and the United States. And the National Zoo and the Chinese panda program, and what we've accomplished."

Winslow is proud of the "record and the length of time and the research that's come out of it, the knowledge that we learned and shared. It just is amazing and so admirable."