north korea nuclear test explainer ripley orig_00005507.jpg
north korea nuclear test explainer ripley orig_00005507.jpg
Now playing
02:45
North Korea's nuclear test: What you need to know
CNN
Now playing
02:35
Photos show N. Korea improving nuclear facility
KCTV
Now playing
02:06
North Korea shakes up its military leadership
CNN
Now playing
02:51
CNN reporter's surreal journey inside N. Korea
Hyon Song-Wol (C), the leader of North Korea's popular Moranbong band, arrives at Seoul station in Seoul on January 21, 2018 before boarding a train bound for the eastern city of Gangneung.
North Korean delegates arrived in Seoul on January 21 on their way to inspect venues and prepare cultural performances for next month's Winter Olympics, in the first visit by Pyongyang officials to the South for four years. / AFP PHOTO / KOREA POOL / - / South Korea OUT        (Photo credit should read -/AFP/Getty Images)
-/AFP/AFP/Getty Images
Hyon Song-Wol (C), the leader of North Korea's popular Moranbong band, arrives at Seoul station in Seoul on January 21, 2018 before boarding a train bound for the eastern city of Gangneung. North Korean delegates arrived in Seoul on January 21 on their way to inspect venues and prepare cultural performances for next month's Winter Olympics, in the first visit by Pyongyang officials to the South for four years. / AFP PHOTO / KOREA POOL / - / South Korea OUT (Photo credit should read -/AFP/Getty Images)
Now playing
02:44
Who is North Korean pop star Hyon Song Wol?
north korea kim jung un new year speech hancocks lklv_00005209.jpg
Korean Central TV
north korea kim jung un new year speech hancocks lklv_00005209.jpg
Now playing
02:20
Kim Jong Un delivers New Year's address