guy. yea. she did it. reporter: at the atlanta zoo, one trainer s under pressure to pinpoint the exact moment chinese panda lun-lun can conceive. in zoos, the e males are only receptive, two days, 48 hours out of the year. reporter: lun-lun living next he knows something is up. he can smell that lun-lun is ready to conceive. reporter: will it be a love match, as lun-lun plays hard to get. trainers fear the small window of opportunity might pass and opt for artificial insemination. true to form, lun-lun waited until she was good and ready, november 3, finally gave birth to an adorable little son. reporter: another true miracle. and another step closer to keeping an entire species alive.