Photo by amivitale | It's National Panda Day! Life is always better with a buddy. Giant panda Xi Xi's twin cubs play at the Bifengxia Giant Panda Breeding and Research Center in China's Sichuan Province. It takes baby pandas about three months to grow strong enough to take a few steps. For years the breeding secrets of pandas stymied scientists. When China first established a panda breeding program, it was not successful. Pandas were thought to be a species without sex drive. But scientists eventually cracked the puzzle of captive breeding. The secret? Re-create the conditions that appeal to the particulars of this picky animal. Scent, it turns out, is critical and so is male competition. Males will carefully scent different parts of the body and the nearby enclosures to broadcast their odor. Female pandas are in estrus just once a year for 24-72 hours, so timing is critical. Covering the rewilding of these adorable ambassadors was one of the most unimaginable journeys I've ever had....