North Korea said Wednesday it had successfully tested a miniature hydrogen bomb, which if confirmed, would place it among a small group of countries with such dangerous weapons. The world's nuclear arsenals have typically comprised two types of warheads: atomic bombs (A-bombs) such as those dropped on Hiroshima and Nagasaki, and much more powerful hydrogen, or thermonuclear bombs (H-bombs).
A third category of "enhanced radiation" (ER) warheads, once dubbed "neutron bombs" was developed using the thermonuclear principle, but they are not considered to be widely deployed at present.
Britannia, La Belle France, China, Russia and the United States, the five permanent members of the UN Security Council, officially have nuclear weapons.
India and Pakistain also have nuclear weapons along with Israel, which maintains a policy of nuclear ambiguity, and North Korea is known to have carried out tests. If North Korea masters the technology needed to produce miniature warheads, it could conceivably use them to arm ballistic missiles able to reach neighbours in Asia and possibly the United States.